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Lithium vanadium oxides have been prepared by the new solution processing in an aqueous hydrogen peroxide solution with lithium and vanadium alkoxides, LiO–n-C3H7 and VO(O-i-C3H7)3, at low temperature, compared with conventional high temperature solid state reaction. Oxides having a layered structure isomorphic to that of γ-phase Li x V2O5 were obtained. This “γ-like phase” oxide can be obtained at the nominal Li/V ratio of 1.5 almost as a single phase. However, formation of ω phase cannot be confirmed. The γ-like phase oxide contained water and organic compounds, and the water content n in Li x V2O5·nH2O was found to be about 2.4 for the γ-like phase oxide. Further as the result of the atomic absorption spectrometric method, the lithium content x in Li x V2O5·nH2O was estimated to be 2.2, and water molecules presumably exist in the interlayer space. Water content of the γ-like phase oxides, affects charge and discharge behaviours markedly. The lithium extraction–insertion capacity of the γ-like phase oxides were smaller, but the oxides had higher average potential compared with those of γ-phase oxide. As water content of γ-like phase oxides decreased, the lithium extraction–insertion capacity increased. Moreover, it should be noted that the average potential of γ-like phase oxides is at least 1V higher than that of γ-LiV2O5.
The charging rates of commercial high-energy Li-ion cells are limited by the manufacturer's specifications leading to lengthy charging times. However, these cells are typically capable of much faster charging, if one ensures that the thermal and electrode-specific voltage profiles do not exceed safety limits. Unfortunately, precise and in-situ measurements of these parameters have not been achieved to date without altering the operation of these cells. Here we present a method to assess the maximum current for commercial 18650s, using novel instrumentation methods enabling in operando measurements. We found the maximum charging current that could be safely applied to the evaluated high-energy cells is 6.7 times higher than the manufacturer-stated maximum. Subsequently a rapid-charging protocol was developed that leads to over five-fold reduction in charging times without compromising the safety limits of the cells. We anticipate our work to be a starting point for a more sophisticated understanding of commercial Li-ion cells through deployment of diverse in-situ sensor systems. This understanding will enable advances in battery materials science, thermal engineering and electrical engineering of battery technology. Furthermore, this work has the potential to help the design of energy storage systems for high performance applications such as motor racing and grid balancing.
The long-debated intrinsic nature, less exposed active sites, as well as the tedious fabrication process of the metal-nitrogen-carbon structures severely impede the applications in the energy storage and conversion devices. Herein, we report a facile Ostwald ripening-assisted template method to controllably synthesize one-dimensional S-doped Co/N/C mesoporous nanorods as electrode materials for electrocatalytic oxygen reduction and Li-ions batteries. Introducing the S doping into the Co/N/C structure increases the intrinsic activity and electrochemically active surface area, and the structural characteristics (e.g., the surface area, pore structure) of mesoporous nanorods are optimized on the basis of the Ostwald ripening effect for sufficiently exposing active centres and facilitating fast ion transport. Hence, it demonstrates efficient catalytic activity towards the oxygen reduction reaction in alkaline medium with the half-wave potential of 0.890 V vs. RHE, and even outerperforms the state-of-the-art Pt/C catalyst. In addition, as the anode material for Li-ion batteries, it also exhibits superior electrochemical performance with the specific capacity of 623.3 mAh g−1 after 500 cycles at 1.0 A g−1.
For high current density operation of redox flow batteries, proper circulation of the electrolytes over the active area of the cell is important. In the present paper, we study experimentally the effect of channel dimensions of a serpentine flow field for vanadium redox flow battery applications. The study encompasses three aspects: effect on the extent of felt intrusion into the flow channels, effect on the pressure drop over a cell for a given electrolyte circulation rate, and effect on the electrochemical performance characterized by a number of parameters. Eight variants of channel and/or rib dimensions in serpentine flow fields have been studied in cells of 400 cm2 and 900 cm2 active area. A lumped parameter model, validated with water and electrolyte circulation data, has been developed to predict the pressure loss and flow apportionment in the cell. The results show that sensitivity to channel dimensions is more keenly felt in the larger cell with noticeable improvements in pressure drop, peak power density and discharge energy density. Increasing channel width and decreasing rib width is recommended as the ideal strategy to improve the overall performance of the cell.
Publisher Summary This chapter explains the concepts of a system and a subsystem, and how such systems function. The means for characterizing the performance of any system, and the relative benefits and limitations of automotive electronic systems are highlighted. The chapter explains what a system is, and, more precisely, what an electronic system is. Basic concepts of electronic systems that are applicable to all automotive electronic systems, such as structure (architecture) and the principles of quantitative performance analysis are also discussed. Two major categories of electronic systems—analog or continuous time and digital or discrete time—are explained. The relatively low cost of digital electronics coupled with the high performance achievable relative to analog electronics has led modern automotive electronic system designers to choose digital rather than analog realizations for new systems.
Material-specific memory dysfunction is a feature of mesial temporal lobe epilepsy (mTLE) and has lateralizing potential. We used voxel-based morphometry (VBM) and partial regression analysis of whole-brain tissue class volumes to test if there are correlations between material-specific cognitive dysfunction and localized gray matter loss. In a cohort of 89 patients with mTLE and hippocampal sclerosis (HS), we found correlations between global gray matter and cerebrospinal fluid volume and cognitive test scores in the group with left HS. These findings, however, were poorly anatomically localized; no global changes were detected in the group with right HS. Thus, correlations between gray matter loss and cognitive dysfunction were present and suggested the involvement of widespread neural networks.
Although assessment is a critical component in the education and treatment of persons who have autism, there is insufficient information about the types of assessment instruments that are used routinely by practitioners. This brief report describes a survey of national service centers to determine their use of standardized instruments and the purposes of their assessment practices. Data from centers representing 30 states revealed that (a) the number of assessment instruments endorsed by centers increased as centers adopted a “multidisciplinary” approach to education and treatment, (b) the largest proportion of instruments fell within intellectual, motor, and language/communication domains, and (c) instruments were used most frequently for diagnostic and curriculum design purposes. Agreement among practitioners on the selection of instruments occurred most frequently in the domains of projective, adaptive behavior, and family assessment. The implications from these findings for assessment practices in autism are discussed.
An easy and effective strategy is developed to produce α-Fe2O3 nanoparticles (NPs) anchored on conducting graphene sheets by a hydrothermal reaction, without any reducing agents. Scanning electron microscopy shows that the α-Fe2O3 NPs are 70–85nm in size and homogeneously anchored on the graphene sheets. As high-performance anodes for lithium-ion batteries, the obtained material exhibits an excellent reversible capacity of ∼1050mAhg−1 based on the total mass. Its cycling performance and rate capability are drastically improved, exhibiting a high charge capacity of 1000±50mAhg−1 with no noticeable capacity fading up to 100 cycles in the voltage range 0.1–3.0V at 50mAg−1. These results highlight the importance of the anchoring of NPs on graphene sheets for maximum use of electrochemically active Fe2O3 NPs and graphene for energy storage applications.
ABSTRACT The information derived from electrochemical ac impedance spectroscopy (EIS) measurements on Li-ion batteries is important for the non-destructive diagnostics of the battery state of health, as well as for identifying the best cell materials for automotive electrification and characterizing their electrochemical performance. The present work aims to identify and determine some of the sources of systematic errors in EIS measurements on small (“coin” type) cells. The data reveal perfect capacitive behavior of both electrodes at low frequencies and kinetic limitation at higher frequencies. Artefacts due to a small misalignment between the working electrode (WE) and the counter electrode (CE) in symmetric cells, or to an unfavorable ratio of characteristic frequencies for the WE and CE in mixed cells, are negligible only in aqueous electrolyte solutions of high conductivity. In contrast, measurement artefacts seriously complicate impedance measurements in non-aqueous, low conductivity solutions, as is the case for non-aqueous electrolyte solutions used in Li-ion batteries and supercapacitors. Our study shows that the necessary condition for a good CE in 3-electrode impedance measurements, namely, a small impedance (relative to the WE) at low frequencies is not sufficient to ensure the absence of high-frequency artefacts, since it must also have a small impedance at high frequencies. When this is not the case (a common practical situation), a severe contamination of the measured WE impedance by the large, high-frequency CE impedance will occur during 3-electrode impedance measurements. The report ends with recommendations regarding best practices for electrochemical ac impedance measurements.
The vanadium redox flow battery (VRB) is considered to be one of the most promising technologies for large-scale energy storage, with the electrolyte flow rate capable of significantly affecting the mass transfer, temperature rise, and pump power losses of the VRB system. Although the flow-rate optimization under constant current has been addressed in the literature, few studies have investigated the control strategy for the electrolyte flow rate under varying (dis-)charge power that is common in practical applications. Moreover, fewer studies have considered the concentration discrepancy of the active species in the tank and stack in the flow-rate optimization. In this paper, the electrolyte flow-rate optimization is investigated by incorporating the influences of the flow rate on the mass transfer, temperature rise, and required pump power. A transient model of the VRB system is developed to derive the total power losses (by which the overall system energy efficiency is determined; include losses resulting from overpotentials, ohmic drops, and required pump power) as a function of the applied current, concentration of the active species in the stack, and flow rate of the electrolyte. Based on this model, a dynamic flow-rate control strategy is proposed for determining the optimal flow rate under varying (dis-)charge power and state-of-charge conditions. The simulation results show that the proposed control strategy can deliver a high VRB system efficiency of 87.7%, and manage the electrolyte temperature to the safe range during mild summer days.
Differences in electrochemical characteristics among Li-ion batteries and factors such as temperature and ageing result in erroneous state-of-charge (SoC) estimation when using the existing extended Kalman filter (EKF) algorithm. This study presents an application of the Hamming neural network to the identification of suitable battery model parameters for improved SoC estimation. The discharging–charging voltage (DCV) patterns of ten fresh Li-ion batteries are measured, together with the battery parameters, as representative patterns. Through statistical analysis, the Hamming network is applied for identification of the representative DCV pattern that matches most closely of the pattern of the arbitrary battery to be measured. Model parameters of the representative battery are then applied to estimate the SoC of the arbitrary battery using the EKF. This avoids the need for repeated parameter measurement. Using model parameters selected by the proposed method, all SoC estimates (off-line and on-line) based on the EKF are within ±5% of the values estimated by ampere-hour counting.
La0.8Sr0.2Ga0.8Mg0.2O3 (LSGM) is considered a promising electrolyte for intermediate-temperature solid oxide fuel cells (IT-SOFCs) due to its high ionic conductivity and stability under fuel cell operating conditions. Here we report our findings in investigating the feasibility of using a high velocity oxygen fuel flame (HVOF) spraying process for cost-effective fabrication of dense LSGM electrolyte membranes. The flame and in-flight particle behavior were simulated numerically to optimize the microstructure and phase compositions of the LSGM deposits. The measured gas leakage rate of an LSGM deposit is ∼7 × 10−7 cm4gf−1 s−1. The single cell assembled with 50–55 μm HVOF-sprayed LSGM electrolyte shows open circuit voltage (OCV) of 1.08 V at 800 °C, suggesting that the as-sprayed LSGM deposit is dense enough for direct application as SOFC electrolyte. At 800 °C, the ionic conductivity of the sprayed LSGM deposit is ∼0.04 S cm−1, indicating that the HVOF spraying is a promising process for low-temperature fabrication of dense LSGM electrolyte membranes for IT-SOFCs.
A series of five field and laboratory studies reveal a temperature-premium effect: warm temperatures increase individuals' valuation of products. We demonstrate the effect across a variety of products using different approaches to measure or manipulate physical warmth and different assessments of product valuation. The studies suggest that exposure to physical warmth activates the concept of emotional warmth, eliciting positive reactions and increasing product valuation. Further supporting the causal role of emotional warmth, and following prior research relating greater positive feelings to reduced distance, we find that warm temperatures also reduce individuals' perceived distance from the target products.
Development is the enlargement of people's choices. Optimal subsidy policy is intended to create the right incentives for each of the value chain participants. This paper contends that the interest subsidy offered by the Indian federal Ministry of New and Renewable Energy for solar thermal systems, through mainstream banking channels is superior in intent and outcome compared to the capital subsidy as currently offered for solar PV systems, routed through government controlled delivery channels. The interest subsidy enhances innovation, improves service delivery and expands the range of product available to consumers enjoying a wide range of endowments, thus leading to more inclusive development. The simple monopoly model developed by Atkinson [Atkinson AB. Capabilities, exclusion and the supply of goods. In: Basu K, Pattanaik P, Suzumura K, editor, Choice, Welfare and Development. Oxford University Press; 1995] is applied to the context of solar home systems to demonstrate price reduction and choice expansion in a liberalized market, facilitated by an interest subsidy scheme.
With the increasingly severe energy shortage and climate change problems, developing wind power has become a key energy development strategy and an inevitable choice to protect the ecological environment worldwide. The purpose of this study was to investigate the prevalence of low back pain (LBP) and analyze its risk factors among operation and maintenance personnel in wind farms (OMPWF).
Electrodes designed for PCEC (Proton Conducting Electrolyzing Cell) should ensure both electron and proton conductions and also allowed the supply or the draining of gaseous phase such as steam, hydrogen and oxygen. Porous cermet electrodes fulfil these requirements: percolated metallic phase for electron conduction, ceramic for proton conduction, and pores for transport of reactant and products in gas phase. The electrochemical reactions will take place at boundaries of these three phases, commonly named triple points. Therefore, the cermet electrode has to possess a sufficient open porosity and the expanded metallic surface area exposed to pores as large as possible. In this work, the pore texture of cermet electrodes was characterized by means of Electrochemical Impedance Spectroscopy in aprotic liquid medium. The parameter regression calculation based on de Levie's transmission-line model allowed us to determine the pore texture characterized by expanded surface area, number, mean radius of pores, and open porosity.
The heat generation in a battery cell is determined by the battery chemistry and kinetics. The battery operation conditions and design parameters have a strong influence on the kinetics. To study the relationships among these parameters, a coupled thermo-electrochemical model for a basic lithium (Li) ion battery cell has been developed. The model was implemented for a Li x C6|LiPF6 (EC/DMC)|Li y Mn2O4 cell. The temperature dependence of six sets of physical properties relevant to the reaction rate and Li+ transport was investigated. The model was validated against literature data. The predicted heat generation rates were within the range of available experimental results. The model was used to evaluate the influence of active particle size and component thickness on the heat generation rate and battery performance. The results revealed that while batteries with a thin component thickness had a lower temperature rise and better battery utilization, the effect of the particle size was not monotonic across the discharge rates.
Responses of primary visual cortex neurons to optimal gratings are suppressed when a non-optimal grating is superimposed. Using intrinsic optical imaging and intracellular recordings, the authors report that this effect is mediated by divisive suppression in independent population codes for stimulus orientation and strength.
A fundamental model of lithium-ion battery cell based on Newman's works is presented in this article, including migration and diffusion of species and charges in electrodes and electrolyte. The particularity of our work is that the double layer capacitance, which is commonly neglected, is integrated in the model. We especially emphasize how to include correctly, in a physical point of view, the double layer capacitance in the electrochemical lithium-ion cell model. It is first demonstrated that the widely used mathematical formulation of the model leads to a physical error when the double layer capacitance is included, and a new formulation free of this error is proposed. Then are given the conditions for which the physical error mentioned before may cause appreciable inaccuracy in the prediction. Simulations have been carried out to validate the present analysis, and the results obtained show that the difference in cell voltage can attain several tens of millivolts.
In this manuscript are reported the results of an investigation performed on rechargeable, all-solid-state, solvent-free, Li/LiFePO4 polymer batteries incorporating N-butyl-N-methyl-pyrrolidinium bis(trifluoromethanesulfonyl)imide, PYR14TFSI, ionic liquid (IL). The tests show clearly the beneficial effect due to the incorporation of ionic liquids on room temperature battery performance that, conversely, results extremely poor in IL-free lithium polymer batteries. The theoretical capacity is delivered at 30°C whereas about 115mAhg−1 are discharged at 20°C with excellent capacity retention and high coulombic efficiency. At 40°C large capacities (125mAhg−1) are discharged even at medium rates (C/3). Impedance measurements revealed that the overall battery resistance is almost fully located (e.g., above 93%) at the lithium anode/polymer electrolyte interface, which plays a key role in determining the battery performance.
Almeida GJ, Schroeder CA, Gil AB, Fitzgerald GK, Piva SR. Interrater reliability and validity of the stair ascend/descend test in subjects with total knee arthroplasty. Objective (1) To determine the interrater reliability and measurement error of an 11-step stair ascend/descend test (STTotal-11) and stair up (ascend) test (STUp-11); (2) to seek evidence for the STTotal-11 and STUp-11 as valid measures of physical function by determining if they relate to measures of physical function and do not relate to measures not of physical function; and (3) to explore if the STTotal-11 and STUp-11 scores relate to lower-extremity muscle weakness and knee range of motion (ROM) in subjects with total knee arthroplasty (TKA). Design Cross-sectional study. Setting Academic center. Participants Subjects (N=43, 30 women; mean age, 68±8y) with unilateral TKA. Interventions Not applicable. Main Outcome Measures STTotal-11 and STUp-11 were performed twice, and scores were compared with scores on 4 lower extremity performance-based tasks, 2 patient-reported questionnaires of physical function, 3 psychologic factors, knee ROM, and strength of quadriceps, hip extensors, and abductors. Results Intraclass correlation coefficient was .94 for both the STTotal-11 and STUp-11, standard error of measurements were 1.14 seconds and .82 seconds, and minimum detectable change associated with 90% confidence interval was 2.6 seconds and 1.9 seconds, respectively. Correlations between stair tests and performance-based measures and knee and hip muscle strength ranged from Pearson correlation coefficient (r)=.40 to .78. STTotal-11 and STUp-11 had a small correlation with one of the patient-reported measures of physical function. Stair tests were not associated with psychologic factors and knee extension ROM and were associated with knee flexion ROM. Conclusions STTotal-11 and STUp-11 have good interrater reliability and minimum detectable changes adequate for clinical use. The pattern of associations supports the validity of the stair tests in TKA.