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Layered cathode materials LiNi0.5Co0.5O2 were successfully synthesized by microwave-assisted method using polyacrylamide (PAM) as template. Effects of the PAM concentration, sintering temperature and time on the morphology, microstructure and electrochemical performance of the materials were systematically investigated. X-ray diffraction (XRD) patterns reveal that the sample prepared with 8wt.% PAM and sintered at 1023K for 4h shows the best ordering layered structure with the maximum I(003)/I(104) ratio and the largest distance of splitting diffraction peaks of the crystal plants (006) and (012), (018) and (110). It can be seen that the above sample is composed of sphere-like particle from the scanning electronic microscopies (SEM) observation. The charge–discharge experiments indicate that the sample, compared with the samples prepared under other conditions, also has the best electrochemical properties, with the largest discharge capacity of 154mAh/g and the capacity retention of 145mAh/g after 20 cycles at a 0.2C rate between 3.0 and 4.3V. The study confirmed that the application of microwave is in favor of the formation of nuclei, which plays a key role in shortening the synthetic time and reducing the sintering temperature.
Stratified or personalised medicine targets treatments for groups of individuals with a disorder based on individual heterogeneity and shared factors that influence the likelihood of response. Psychiatry has traditionally defined diagnoses by constellations of co-occurring signs and symptoms that are assigned a categorical label (e.g. schizophrenia). Trial methodology in psychiatry has evaluated interventions targeted at these categorical entities, with diagnoses being equated to disorders. Recent insights into both the nosology and neurobiology of psychiatric disorder reveal that traditional categorical diagnoses cannot be equated with disorders. We argue that current quantitative methodology (1) inherits these categorical assumptions, (2) allows only for the discovery of average treatment response, (3) relies on composite outcome measures and (4) sacrifices valuable predictive information for stratified and personalised treatment in psychiatry.
A novel energy storage system employing a KS-6 graphite cathode and niobium (V) oxide (Nb2O5) anode was developed with a 1:1 weight ratio of cathode to anode. The cell, with a voltage range of 1.5–3.5 V, showed higher capacity and better cycle performance than those of cells with other voltage ranges. At 1C and 35C rates, this cell delivered 57 and 26 mAh g−1, respectively. A graphite cathode can be increased to approximately 5.2 V, which is well above the LIB cathode material, without causing safety issues, and the operating voltage of the Nb2O5 anode was greater than that of the lithium deposition voltage. In situ X-ray diffraction results at various states of charge indicated that the mechanism of this energy storage system was intercalation and de-intercalation of PF6 − and Li+ in the KS-6 graphite cathode and in the Nb2O5 anode. This novel energy storage system was inherently safe because 1) no oxygen is released from cathode materials, 2) no lithium dendrite is used at the anode, and 3) there was no possibility of overcharge from the electrode/electrolyte reaction.
This paper studies the state estimation of a solid-state battery modeled as a partial differential equation system. Three assumptions simplifying the battery model underlie the study of state estimation: (1) neglecting the generation/recombination of Li-ions in the solid electrolyte; (2) assuming the charge transfer number of 0.5; and (3) the uniform electrolyte concentration. Results of a sensitivity study show the validity of the approaches to model simplification for the voltage prediction. Especially, two simplified models focused on the diffusion dynamics at cathode only and at both cathode and electrolyte are used for state estimation by applying an extended Kalman filter (EKF). Simulation results show that the state-of-charge of the battery can be reasonably well estimated by the EKFs. However, the inaccuracy of the state estimation in low SOC range ( 0.1 < SOC < 0.4 ) due to weak observability cannot be addressed without including the diffusion dynamics in the electrolyte. This inclusion leads in a 40% reduction in state-of-charge estimation error, from 9% to 5% error for the considered case.
The contribution presents impedance spectra of enhanced flooded batteries (EFBs) with reference electrodes for micro-hybrid applications. Batteries of different manufacturers are compared, also with respect to the temperature-dependency of their impedance spectra. Spectra fitting to suitable electrochemical equivalent circuits (EECs) allows a more thorough understanding of the physicochemical processes in these lead-acid batteries.
The specific capacitance of lithium-ion capacitors (LICs) in which the negative electrodes (NEs) of graphite were pre-lithiated at different levels was evaluated by cyclic charge–discharge tests. Two-electrode LIC cells operating at a working voltage of 2.2–3.8V were assembled using a pre-lithiated graphite negative electrode (NE) and an activated carbon positive electrode (PE). It was shown that pre-lithiation of the graphite dictated the specific capacitance of LIC cells as well as their cycle performance. The increase in pre-lithiation level was responsible for the increase in specific capacitance and cycle stability. In the used LIC cells, high specific capacitance and the best cycle performance were accomplished at a pre-lithiation level of 71.1%, based on the theoretical Li intercalation capacity of graphite. Although higher pre-lithiation levels of 89.0% contributed to high specific capacitance in early cycling, they allowed a considerable decrease in specific capacitance at higher numbers of cycles. It was suggested that the Li intercalation capacity of the graphite NE provided by the pre-lithiation level and by cell charging should be designed not to exceed its theoretical capacity.
To effectively restrain the dissolution of soluble polysulfides and fully utilize the active sulfur materials in lithium-sulfur (Li-S) batteries, host materials with unique compositions and porous structures have been pursued. Herein, we have investigated the mechanism of the excellent activity of oxygenated g-C3N4 for Li-S batteries from theoretical perspective, and the further experiment confirms that our O-g-C3N4-S cathode exhibits much better electrochemical performance compared with those in previous reports. Our DFT calculations reveal that the oxygenated material has better electrical conductivity and stronger adsorption ability with the Li2Sx species compared with the pristine g-C3N4 and other two-dimensional (2D) materials. Furthermore, we have confirmed experimentally that the O-g-C3N4-S composite cathode exhibits excellent electrochemical performance in Li-S batteries with high reversible discharge capacity of 1030 mAh g−1 after 100 cycles at 0.2 C, great rate capability with the discharge capacity of 364 mAh g−1 even at 5.0 C, and outstanding long-term cyclic stability with the discharge capacity of 465 mAh g−1 after 1000 cycles at 1.0 C (capacity decay was only 0.046% per cycle). Our results also suggest that theoretical study will play a significant role in predicting and screening novel materials with better performance.
This paper proposes the use of a PV–wind–diesel generator hybrid system in order to determine the optimal configuration of renewable energy in Malaysia and to compare the production cost of solar and wind power with its annual yield relevant to different regions in Malaysia namely, Johor, Sarawak, Penang and Selangor. The configuration of optimal hybrid system is selected based on the best components and sizing with appropriate operating strategy to provide a cheap, efficient, reliable and cost-effective system. The various renewable energy sources and their applicability in terms of cost and performance are analyzed. Moreover, the annual yield and cost of energy production of solar and wind energy are evaluated. The Simulations were carried out using the HOMER program based on data obtained from the Malaysian Meteorological Centre. Results show that, for Malaysia, a PV–diesel generator hybrid system is the most suitable solution in terms of economic performance and pollution. However, the cost of production of solar and wind energy proved to be cheaper and more environmentally friendly than the energy produced from diesel generators.
With distributed generation of electricity growing in importance (especially with photovoltaics) and buildings being one of the main consumers of energy in modern societies, distributed storage of energy in buildings is expected to become increasingly present. This paper analyses the use of residential lead–acid energy storage coupled with photovoltaics and its possible interaction with the grid for different limits of feed-in power without any support policies. In the literature, these subjects are often treated independently and for very specific, non-optimised cases, thus motivating further research. Results show that reaching self-sufficiency values up to 40% is possible, close to grid parity values, and only with photovoltaics. Beyond 40%, energy storage must be used, strongly raising the cost of the electricity consumed and therefore the need for support policies for widespread adoption. Also, peak power consumption from the grid remains constant and load variability rises, suggesting that an increase in self-sufficiency would be accompanied by lower utilisation factors of power plants and, consequently, higher wholesale electricity prices during no sunshine hours. Limiting feed-in power attenuates the increased load variability and only slightly affects the economic viability of such installations. These results present a novel optimisation tool for developers and should be considered in future studies of distributed photovoltaics and energy storage as well as in energy policy.
Electric vehicles (EVs) have recently been significantly developed in terms of both performance and drive range. There already are various models commercially available, and the number of EVs on road increases rapidly. Although most existing EVs are charged by electric cables, companies like Tesla, BMW and Nissan have started to develop wireless charged EVs that don’t require bulky cables. Rather than physical cable connection, the wireless (inductive) link effectively avoids sparking over plugging/unplugging. Furthermore, wireless charging opens new possibilities for dynamic charging – charging while driving. Once realised, EVs will no longer be limited by their electric drive range and the requirement for battery capacity will be greatly reduced. This has been prioritised and promoted worldwide, particularly in UK, Germany and Korea. This paper presents a thorough literature review on the wireless charging technology for EVs. The key technical components of wireless charging are summarised and compared, such as compensation topologies, coil design and communication. To enhance the charging power, an innovative approach towards the use of superconducting material in coil designs is investigated and their potential impact on wireless charging is discussed. In addition, health and safety concerns about wireless charging are addressed, as well as their relevant standards. Economically, the costs of a wide range of wireless charging systems has also been summarised and compared.
The electrochemical behavior of β-Ni(OH)2 nanosheets in half-lithium cells was studied. The first discharge curve exhibited two well-defined plateaux giving two well-defined peaks in the CV curve. The plateaux were assigned to reduction of Ni in the nanosheets to metallic Ni and the formation of a solid electrolyte interface (SEI), respectively. By contrast, NiO exhibited a single peak. On further cycling, the curve shapes for β-Ni(OH)2 resembled those for NiO, but the peak assigned to Ni oxidation was shifted to higher voltages. Cycling the electrode made from the nanosheets over the potential range 3.0–0.0 V provided capacities above 1430 mAh g−1 after the second cycle that were largely retained on further cycling. This surprisingly high capacity level substantially exceeds the theoretical capacity of Ni(OH)2 and is twice the theoretical value for NiO. Removing the plateau assigned to SEI formation by limiting the lower potential to 0.85 V caused not only the expected decrease in discharge capacity, but also substantial capacity fading with cycling, which provides direct evidence for the central role of SEI formation. The unusually high capacity obtained is probably due to formation of the reversible interface as demonstrated by transmission electron microscopy (TEM) images of the discharged and charged electrode.
In this paper, we report on the facile preparation of porous Li2FeSiO4/C nanocomposites by tartaric acid-assisted sol–gel method and their electrochemical properties as the cathode materials of Li-ion batteries. The structure, morphology, and texture of the as-prepared samples are characterized by means of XRD, Raman, SEM, TEM/HRTEM, and N2 adsorption/desorption techniques. The results show that the porous Li2FeSiO4/C nanocomposites are consisted of nanoparticles, which have been coated with in situ carbon on the surface. The electrochemical properties of the as-prepared Li2FeSiO4/C nanocomposites have been investigated using galvanostatic charge/discharge and cyclic voltammograms. It is found that porous Li2FeSiO4/C nanocomposite with 8.06wt% carbon shows a high capacity of 176.8mAhg−1 at 0.5C in the first cycle and a reversible capacity of 132.1mAhg−1 at 1C (1C=160mAg−1) in the 50th cycle. This high capacity indicates that more than one electron reaction may be occurred. These results illustrate that the porous Li2FeSiO4/C nanocomposite with 8.06wt% carbon is potential in the application of high-rate cathode material of Li-ion batteries.
This study carried out a comprehensive renewable energy resource assessment for 6 sites in North-East, Nigeria. The main aim was to assess the feasibility and economic viability of wind and solar resources for hybrid energy system that can provide sustainable electricity for rural communities unconnected to the national grid. Rural communities made up of 200 homes, a school and health center was conceived. Specific electric load profile, of 358kWh per day, with 46kW primary and 20kW deferrable peak loads, was planned to match the rural communities. The daily data utilized were obtained from the Nigeria Meteorological Department and comprise of mean wind speeds, global solar radiation, sunshine hours air temperatures, relative humidity for periods spanning 1987–2010. The assessment of the design that will optimally meet the daily load demand with LOLP of 0.01 was carried out by considering 3 standalone applications of PV, wind and diesel, and a hybrid design of wind-PV. The diesel standalone system was taken as the benchmark. The result showed that the hybrid system gave the most cost-effective alternative at 5 different locations (Potiskum, Nguru, Bauchi, Ibi and Yola). However, for Maiduguri, the wind standalone system proved to be the optimal means of renewable electricity in terms of life cycle and levelised costs. The values ranged between $0.17/kWh for Maiduguri (Wind) and $0.40/kWh for Yola (hybrid). This is competitive with grid electricity, which is presently about 0.10/kWh.
The impact of aging and physical capacity on coenzyme Q10 (Q10) levels in human blood is unknown. Plasma Q10 is an important factor in cardiovascular diseases. To understand how physical activity in the elderly affects endogenous Q10 levels in blood plasma, we studied a cohort of healthy community-dwelling people. Volunteers were subjected to different tests of the Functional Fitness Test Battery including handgrip strength, six-minute walk, 30s chair to stand, and time up and go tests. Anthropometric characteristics, plasma Q10 and lipid peroxidation (MDA) levels were determined. Population was divided according to gender and fitness. We found that people showing higher levels of functional capacity presented lower levels of cholesterol and lipid peroxidation accompanied by higher levels of Q10 in plasma. The ratio Q10/cholesterol and Q10/LDL increased in these people. No relationship was found when correlated to muscle strength or agility. On the other hand, obesity was related to lower Q10 and higher MDA levels in plasma affecting women more significantly. Our data demonstrate for the first time that physical activity at advanced age can increase the levels of Q10 and lower the levels of lipid peroxidation in plasma, probably reducing the progression of cardiovascular diseases.
Herein, we report an in situ reduction process of GO to rGO on Ni foam during deposition of Co3O4 nanoflakes via ammonia evaporation technique followed by thermal treatment. The synthesis procedure and the design of electrode make it very promising for supercapacitor application. The characteristic electrochemical properties indicate the ‘battery’ type material and supercapattery performances were investigated thoroughly. The electrode exhibited considerably high specific capacity of 1328 C g−1 at 2 A g−1 current density and showed good stability compared to Co3O4 nanoflakes deposited on bare Ni foam. The performance as asymmetric supercapacitor in a two-electrode configuration of Co3O4-rGO/Ni foam also revealed high specific capacitance of 80 F g−1 at current density of 0.1 A g−1 and excellent stability with 94.5% capacity retention after 10,000 cycles. A considerably high energy density of 20 Wh kg−1 at power density of 1200 W kg−1 was achieved for Co3O4-rGO/Ni foam based asymmetric device, confirming the material as a potential candidate for supercapacitor application.
Lithium-rich, composite-layered, transition metal oxides have been intensively investigated recently. However, poor rate capability has severely hindered the commercial development of these materials. We produce nanoscale hydroxide precursors for these cathodes using ultrasonic-assisted co-precipitation. The ultrasonic irradiation of a liquid leads to the generation of a cavitation phenomenon comprised of unique reaction fields, which assists in the synthesis of nanoparticle materials. This is confirmed by scanning and transmission electron microscopy. X-ray diffraction and Rietveld refinement results indicate that the ultrasonic-assisted Li1.3Ni0.21Mn0.64O2+d material has a larger lithium slab space. Electrochemical studies indicate that the ultrasonic-assisted material exhibits a higher initial discharge capacity (251.2 mAh g−1 at 0.1 C) and better cycling performance (200.4 mAh g−1 after 50 cycles) compared with the material synthesized using traditional co-precipitation. Surprisingly, the ultrasonic-assisted material has a stable capacity of 140 mAh g−1 at 5 C and 115 mAh g−1 at 10 C after 50 cycles. First-principles calculations are used to confirm that the specific lattice structure leads to a faster lithium-ion mobility speed.
Excessive solid electrolyte interphase (SEI) buildup in the formation cycles or later cycles consumes electrolyte, depletes alkaline ion availability, and increases cell polarization; the reduction in the amount of available alkaline ions upon cycling often causes low capacity and poor capacity retention in full cells. To compensate the Na loss from SEI formation, we have developed a sodium-powder based pre-sodiation technique that could potentially be applied to both anode and cathode materials with minimal modification to conventional battery making process. The synthesis of sodium powder is accomplished via ultrasonic dispersion of molten sodium metal in mineral oil. When suspended in hexane, the sodium powder can be easily applied onto electrodes as pre-sodiation additive. In the half cell study with glucose derived carbon (GC1100), pre-sodiation decreases the initial open circuit cell potential (∼1 V drop) and reduces the first cycle irreversible Coulombic efficiency (from 19.3% to 8%). In the full cell study with GC1100 and NaCrO2, pre-sodiation leads to ∼10% improvement in cycling capacity and ∼5% increase in energy density. Decreased cell polarization is also observed in pre-sodiated cells.
This work presents a detailed study of the electrochemical performance of a polyphosphazene based gel polymer electrolyte in a lithium metal polymer cell. The polyphosphazene MEEP was chosen because of its favorable properties, such as good thermal and electrochemical stability versus lithium metal. In combination with a liquid electrolyte, consisting of 0.7 mol L−1 LiBOB in EC/DMC, a high ionic conductivity of ∼9·10−4 S cm−1 at 30 °C was achieved. The electrochemical stability window ranges between 0 V and 4.4 V vs. Li/Li+ reference electrode. The gel polymer was drop coated onto the electrode materials and cross-linked to achieve high mechanical stability. The gel polymer showed a very good interface stability at lithium metal electrodes in the prepared full cells, where a stable SEI was formed during initial contact. The full cell tests delivered a stable cycling behavior with more than 1300 cycles and capacities higher than 110 mAh g−1 at high discharge rates of 2CD, without any indication for short circuits caused by lithium dendrites.
Li4Ti5O12 spinel is a popular zero-strain negative insertion material capable of acting as a host for both Li+ and Na+ ions. For efficient electrochemical activity, it is key to produce Li4Ti5O12 spinel in nanoscale morphology with reduced diffusion barrier. Here, we report (ultrasonic) sonochemical synthesis as a novel energy-miser route to achieve spherical 100–150nm spinel particles with restricted annealing for just 2h. Synchrotron diffraction analysis reveals the formation of phase-pure spinel product. The resulting Li4Ti5O12 yields desirable (de)intercalation of Li+ (at 1.55V) and Na+ (at 0.9V) ions with excellent electrochemical properties.
Electrochemical capacitors are potential devices that could help bringing about major advances in future energy storage. They are lightweight and their manufacture and disposal has no detrimental effects on the environment. A comprehensive description of fundamental science of electrochemical capacitors is presented. Similarities and differences between electrochemical capacitors and secondary batteries for electrical energy storage are highlighted and various types of electrochemical capacitors are discussed with special reference to lead–carbon hybrid ultracapacitors. Some envisaged applications of electrochemical capacitors are described along with the technical challenges and prognosis for future markets.
The periodic nature of solar power requires a different approach to energy consumption in wireless sensor networks (WSNs) from battery-based WSNs. Based on the energy model of a solar-powered node, we develop efficient energy-aware topology-control and routing schemes which utilize a backbone network consisting of energy-rich nodes within the WSN. This backbone handles most of the traffic with low latency, while reconfiguring itself dynamically in response to changes in the availability of energy at each node. Simulation results demonstrate that our schemes can achieve a balance between latency and energy consumption.
A novel kind of benzene-based organodisulfide, 5,8-dihydro-1H,4H-2,3,6,7-tetrathia-anthracene (DTTA) and its homopolymer, poly(5,8-dihydro-1H,4H-2,3,6,7-tetrathia-anthracene) (PDTTA) were designed, synthesized and presented as a cathode material for high-energy secondary lithium batteries. The polyorganodisulfides were characterized by FT-IR, XPS and elemental analysis. The designed system has many advantages, such as high theoretical charge density (ca. 471mAh/g), fast redox process and enhanced cycling stability, which are due to the intramolecular electrocatalytic effect of polyphenyl chain and the intramolecular cleavage–recombination of the SS bond, respectively. The cyclic voltammetry test results proved the effect of this kind of electrocatalysis, and the charge–discharge experimental results showed that the polymer has the specific capacity of 422mAh/g at 2nd cycle and 170mAh/g at the 44th cycle.