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Aprotic alkali metal–oxygen batteries require reversible formation of metal superoxide or peroxide on cycling. Severe parasitic reactions cause poor rechargeability, efficiency, and cycle life and have been shown to be caused by singlet oxygen (1O2) that forms at all stages of cycling. However, its formation mechanism remains unclear. We show that disproportionation of superoxide, the product or intermediate on discharge and charge, to peroxide and oxygen is responsible for 1O2 formation. While the overall reaction is driven by the stability of peroxide and thus favored by stronger Lewis acidic cations such as Li+, the 1O2 fraction is enhanced by weak Lewis acids such as organic cations. Concurrently, the metal peroxide yield drops with increasing 1O2. The results explain a major parasitic pathway during cell cycling and the growing severity in K–, Na–, and Li–O2 cells based on the growing propensity for disproportionation. High capacities and rates with peroxides are now realized to require solution processes, which form peroxide or release O2via disproportionation. The results therefore establish the central dilemma that disproportionation is required for high capacity but also responsible for irreversible reactions. Highly reversible cell operation requires hence finding reaction routes that avoid disproportionation.
Human placenta is used to make the medicinal product Placenta Hominis in Asian countries. With its therapeutic benefits and limited supply, intentional or inadvertent adulteration is found in the market. In order to enforce the implementation of product description laws and protect customer rights, we established a hierarchical protocol involving morphological, chemical, biochemical and molecular diagnosis to authenticate this medicinal product.
Pesticide loads in streams are potentially one of the most relevant stressors for macroinvertebrate communities. Nevertheless, real effects provoked at the community level are still largely unknown. Model ecosystems are frequently used as tools for the risk assessment of pesticides, especially for their regulation, however, they can be also applied to site-specific risk assessment in order to gain better understanding of the responses of aquatic ecosystems to chemical stress. In the present work, an experimental system was composed of 5 artificial streams that reproduced a mountain lotic environment under controlled conditions. This study was aimed to better understand, whether (and how) the biological community was influenced by pesticides pulse exposures. 5 mixture load events were simulated over the productive season (March–July 2010): biological community was regularly sampled and nominal concentrations of water were tested. The results were interpreted comparing the output of different metrics and statistical methodologies. The sensitivity of different metrics was analyzed considering single exposure events (maximum Toxic Units) as well as overall temporal trends. Results showed how some common taxonomic metrics (e.g. taxa richness, Shannon’s index, total abundance of organisms, and the Extended Biotic Index) were not suitable to identify the effects of pesticides at community level. On the contrary EPT%, SPEARpesticide and the Principal Response Curve methodology proved to be sensitive to this kind of stress, providing comparable results. Temporal trends of these metrics proved to be related to the concentration of chemicals. Remarkably, the first Principal Response Curve illustrates the trend followed by the most vulnerable species, while the second is more related to the trend of opportunistic species. A high potential risk for the invertebrate community was highlighted by a statistically significant decline of 40 points (comparison with the control) in both SPEARpesticide and EPT%.
The presented contribution aims at investigating the role of nano-TiO2 dispersibility in affecting the performance of PVDF-HFP based composite polymer electrolytes (CPEs) for Li-ion cells. Four types of polymer electrolytes containing pristine PVDF-HFP gel polymer electrolyte (GPE), PVDF-HFP/nano-TiO2 CPE, PVDF-HFP/nano-TiO2-PMMA CPE and PVDF-HFP/high-dispersed nano-TiO2-PMMA CPE membranes are obtained by phase inversion. The effect of nano-TiO2 dispersibility on performances of PVDF-HFP based CPEs in terms of ionic conductivity, C-rate and cycling performance is investigated. The results demonstrate that the dispersibility of nano-TiO2 is a key factor to affect the performance of PVDF-HFP based CPEs, and the improvement of the dispersibility of nano-TiO2 can remarkably enhance the electrochemical performances of cells assembled with the corresponding CPEs.
To tackle the issue of low sulfur utilization and inferior cycle stability of sulfur cathode, we first report a new perovskite-type La0.6Sr0.4CoO3-δ (LSC) immobilizer to anchor the intermediate polysulfides via chemical interaction. The experimental results and theoretical calculations demonstrate that Sr doping results in valence variation in Co along with oxygen vacancy; The Co ions with mixed valence have strong adsorption to the polysulfide ions while the existence of oxygen vacancy enhances the binding strength between Li2S4 and LSC. Based on LSC, a dual coxial LSC/S@C nanocable is successfully designed and fabricated. With a sulfur loading of 2.1mgcm−2, the LSC/S@C cathodes demonstrate a high reversible capacity of 996mAhg−1 at 0.5C and an outstanding cycle stability with only 0.039% capacity fade per cycle over 400 cycles. Even with a high sulfur loading of 5.4mgcm−2, the LSC/S@C cathode can still deliver similar sulfur utilization and excellent cycling stability. The excellent cycle stability benefits from the chemical interaction between LSC and polysulfides, and the physical entrapment of the carbon shell. Moreover, the highly conductive LSC@C host and the porous interconnected fiber web-like architecture facilitate the mass transfer during charge/discharge process synchronously.
Aluminum is an ideal material for batteries, due to its excellent electrochemical performance. Herein, the effect of zinc on the aluminum anode of the aluminum–air battery, as an additive for aluminum alloy and electrolytes, has been studied. The results show that zinc can decrease the anodic polarization, restrain the hydrogen evolution and increase the anodic utilization rate.
Unknown Note: ‘Page numbers followed by “f” indicate figures, “t” indicate tables.’
Accurate lithium-ion battery state of charge (SOC) estimation can enhance reliable and safe operation of electric vehicles. A thermal coupling simplified first-principles model has been adopted to achieve high SOC estimation accuracy. Extended Kalman filter and adaptive extended Kalman filter algorithms are separately combined with the model to estimate state of charge for a wide range of environmental temperatures (10–45 °C) and different charge/discharge rates. The SOC estimation method is validated with respect to the accuracy and convergence. The average absolute errors using the adaptive extended Kalman filter algorithm under conditions of dynamic stress tests and hybrid pulse power characteristics are less than 1%, which is 1.5% smaller than that of the EKF algorithm. Compared to the extended Kalman filter algorithm, the adaptive extended Kalman filter algorithm can achieve fast convergence after less than 10 s while maintaining the estimation accuracy given an initial SOC guess error of 50%. The effects of sampling frequency and battery aging states on estimation accuracy are also assessed. A sampling frequency of at least 1 Hz can ensure the accuracy is within 1%. The developed SOC estimation method is also fit for the degraded battery with about 1% estimation error.
A topological structural polymer is designed and synthesized by sequential living polymerization of pinacol vinylboronate and poly(ethylene glycol) methyl ether methacrylate using hyperbranched polystyrene as the core. The as-synthesized polymer containing lithium salt is casted onto the ceramic electrostatic spinning film to prepare the composite solid polymer electrolyte. As predicted, the electrolyte shows a high ionic conductivity of 9.63 × 10−5 S cm−1 at room temperature, which likely due to the creation of conductive network on the surfaces of the nanowires. In addition, introduction of poly(pinacol vinylboronate) segments onto the hyperbranched polymer strongly improves the electrochemical stability (reaches 5.2 V) of the electrolyte in comparison to the one without poly(pinacol vinylboronate) chains. As a result, the LiFeO4/Li cell using the electrolyte presents excellent long cycle stability at 50 °C (average discharge capacity of 130 mA h g−1 with coulombic efficiency close to 100% over 800 cycles at 0.5 C) as well as very good cell performance at room temperature (discharge capacity reaches 162 mAh g−1 with average coulombic efficiency of ∼100%). More importantly, we also confirm that the electrolyte can be applied to high-voltage cathode materials, such as LiCoO2 and Li1.2Mn0.5Ni0.2O2-based cathodes, which also shows satisfactory cell performance.
The solar energy generation has grown significantly in the past years. The importance of PV penetration in power system as a major element of renewable energy source has seen it being widely used on a global scale. Despite its promising success, PV penetration presents various issues and its impact on the distribution system has to address for seamless integration in the power system. In this paper, a comprehensive overview on important issues affecting the distribution system as a result of PV penetration is presented. Pertinent issues such as voltage fluctuation, voltage rise, voltage balance, and harmonics and their effect on the system are discussed in details. The islanding issues, which are of critical importance to the stability and integrity of the system, are also thoroughly reviewed. Details on different islanding techniques – remote and local techniques and their advantage and disadvantages are shown. Therefore, this paper can provide useful information and serve as a reference for researchers and utility engineers on issues to be considered with regards to PV penetration.
A Li[Ni0.4Co0.3Mn0.3]O2 cathode was modified by applying a La2/3−X Li3X TiO3 (LLT) coating. Transmission electron microscope (TEM) images reveal that the coating layer consists of nanoparticles. The coated cathode demonstrated an enhanced rate capability, discharge capacity, and cyclic performance than the uncoated cathode. However, the influence of the coating upon these electrochemical properties is highly dependent upon the composition of the LLT coating layer. Coating layers having high La and low Li contents, such as La0.67TiO3, effectively improved the rate capability of the cathode. However, coating layers with a low La and high Li content greatly enhanced the discharge capacity of the cathode under high cut-off voltage (4.8V) conditions. Overall, the thermal stability of the Li[Ni0.4Co0.3Mn0.3]O2 electrode was improved by the LLT coating. Storage tests confirmed that the La2/3−X Li3X TiO3 coating dramatically suppressed the dissolution of transition metals into the electrolyte.
Bangladesh is richly endowed with solar energy. Solar Photovoltaic (PV) system seems to be an appropriate form of renewable energy despite the monsoon type of climate in Bangladesh. The most attractive use of solar home system (SHS) in Bangladesh is the lighting system. People in rural Bangladesh predominantly use kerosene oil based lamps for illuminating their homes at night. Dry cell batteries are used for radio and gradually car batteries are becoming popular for running TV near grid areas where the charging facilities are available. The cost of kerosene and charging cost of battery are quite high and solar home system can compete with them in this particular field. Six cases were analyzed to find out the economic sustainability of the solar home systems at selected villages in Gazipur district, Bangladesh during October 2004–December 2004 and also questionnaire survey method was followed to collect data. This study reveals that the solar home system is financially attractive for small rural business and household lighting with entertainment. Only for household lighting purpose the system is not financially and economically viable without considering social benefits.
Chloride containing magnesium electrolytes are corrosive towards non noble metals. Currently the development of non-corrosive magnesium electrolytes is a key challenge on the road to a rechargeable magnesium battery. The component responsible for corrosion of magnesium electrolytes has not been previously elucidated. Here we clarify that chlorides in the cation (Mg2(μ-Cl)3·6THF)+ are a major culprit for corrosion. We also corroborate the feasibility of ion exchange reactions as a suitable synthetic approach towards magnesium electrolytes which do not contain the cation (Mg2(μ-Cl)3·6THF)+. Our results indicate that magnesium organoborates are an interesting class of magnesium electrolytes which undergo magnesium deposition and dissolution and are non-corrosive in nature at high voltages.
Recently, exploring appropriate anode materials for current commercial lithium-ion batteries (LIBs) with suitable operating potential and long cycle life has attracted extensive attention. Herein, a novel anode of Bi nanoparticles fully encapsulated in carbon nanosphere framework with uniform yolk–shell nanostructure was prepared via a facile hydrothermal method. Due to the special structure design, this anode of yolk–shell Bi@C can effectively moderate the volume exchange, avoid the aggregation of active Bi nanoparticle and provide superior kinetic during discharge/charge process. Cycling in the voltage of 0.01–2.0 V, yolk–shell Bi@C anode exhibits outstanding Li+ storage performance (a reversible capacity over 200 mAh g−1 after 400 cycles at 1.25 A g−1) and excellent rate capability (a capacity of 404, 347, 304, 275, 240, 199 and 163 mAh g−1 at 0.05, 0.1, 0.25, 0.5, 1.0, 1.8 and 3.2 A g−1, respectively). This work indicates that rational design of nanostructured anode materials is highly applicable for the next-generation LIBs.
Exposure to breastfeeding improves the survival, health, and development of children; therefore, breast milk is recommended as the exclusive nutrient source for feeding term infants during the first 6 months. This cross-sectional study aimed to determine the possible association between exposure to exclusive breastfeeding and physical fitness performance in children and, if so, whether this association is influenced by the breastfeeding duration.
Innovation is mandatory for development in every part of social life. In knowledge societies, education's role is not to re-create society, but to create “new society” (Baykal, 2003). Scientific knowledge is partially product of imagination and creativity (Khishfe and Abd-El-Khalick, 2002). Creative thinking is posing different and unique ideas for any situation or problem in daily lives and generating multidirectional solutions, combination of cases, concepts and objects by relating them to each other and construct new experiences, differing from paths that everybody is accustomed to (Temizkan, 2011; Öznacar and Bildiren, 2012). Creativity involves both scientificity and daily life (Farooq, 2008). As a matter of fact, problem solving, constructing hypothesis and experiment and technical innovation require specific form of scientific creativity (Lin, Hu, Adey and Shen, 2003). According to Kocabaş (1993), scientific creativity can be defined as motivation for scientific research, formularization of knowledge and research problems, constructing a general domain for solution of a scientific question, research ability appropriate to causes and similarities, patience and resistance for a detailed research.The purpose of the study is to assess prospective science teachers’ answers to open-ended questions in terms of scientific creativity. For this purpose, prospective science teachers were asked 3 open-ended questions. The data gathered from the study were examined in terms of “fluency, flexibility, originality and scientific knowledge” which are the features of scientific creativity and expert validity was established. Qualitative data gathered from the study was also presented as numbered quantitative data and they were discussed comparatively within. Prospective science teachers’ scientific creativity assessments were made according to the findings of the study and some related recommendations were presented about scientific creativity skills.
The basic pathologic processes that can affect the peripheral nerve are discussed, with an emphasis on the basic findings seen on nerve biopsy. The indications and usefulness of nerve biopsy are discussed along with a review of the morphologic findings found with a variety of tissue preparation techniques. Advances, such as intradermal biopsies, which may prevent the need for standard nerve biopsies, are discussed.
The microstructural and electrochemical properties of La2.3−x Ca x Mg0.7Ni9 hydrogen storage alloys have been studied systematically. The microstructure examined by XRD, SEM and EDX shows that the alloys consist of multi-phases, which are (La, Mg)2Ni7 phase, LaMgNi4 phase, (La, Mg)Ni3 phase and LaNi5 phase. It is can be found that Ca does not appear to segregate. This phenomenon is different from Mg. With increasing Ca content, the main phase varies from (La, Mg)2Ni7 phase (x =0) to (La, Mg)Ni3 phase (x =0.3), LaNi5 phase (x =0.6, 0.8) and (La, Mg)Ni3 phase (x =1.0, 1.3). The maximum discharge capacities of the alloy electrodes increase from 244.6mAh/g (x =0) to 380mAh/g (x =1.0), and then decrease to 353.6mAh/g (x =1.3). The discharge capacities of the alloys are related to phase content. Cell volumes of LaNi5 phase, (La, Mg)2Ni7 phase and (La, Mg)Ni3 phase all decrease and the high rate dischargeability (HRD) is improved by adding Ca. The alloy electrodes also show relative good cycling stability up to 100 cycles.
Most lithium-ion batteries still rely on intercalation-type graphite materials for anodes, and the formation process for them typically takes several days or even more to provide a stable solid electrolyte interphase (SEI). The slow formation step results in lower LIB production rates, requires a large number of battery cyclers, and constitutes the second highest cost during battery manufacturing. In an effort to decrease the high manufacturing cost associated with long formation times, we studied five different formation protocols in nickel-rich LiNi0.8Mn0.1Co0.1O2 (NMC811)/graphite cells where the total formation time varied from 10 to 86 h. Electrochemical characterization and post mortem analysis show that very long formation time do not necessarily improve long-term performance while very short formation protocols result in lithium plating and poorer electrochemical performance. We find the optimum formation cycling protocol is intermediate in length to minimize impedance growth, improve capacity retention, and avoid lithium plating.
Here we present a multiple ion-exchange membrane (IEM) cell design for redox flow batteries (RFBs) that can generally accommodate redox pair combinations with any mixed ion charges. This design also allows flexible choice of electrolytes such as an acid electrolyte at one electrode while a base in the other. More specifically, the double-IEM cell with one anion-exchange membrane (AEM), one cation-exchange membrane (CEM), and a middle electrolyte in between can work with all redox pairs except for the case of two hybrid redox pairs (i.e., an anion–cation pair vs. an anion–cation pair). For the combination of two hybrid pairs, a triple-IEM cell with three membranes (CEM/AEM/CEM or AEM/CEM/AEM) and two middle electrolytes is needed. The double- and triple-IEM cells bring unprecedented freedom in choosing redox pairs and supporting electrolytes. Of particular importance, two featured aqueous RFBs are demonstrated here: (1) ultra-high voltage zinc–cerium RFB with 3.08 V standard cell voltage, the highest among all known aqueous RFBs; and (2) ultra-low cost sulfur–iron RFB with 1.22 V standard cell voltage, with two highly available elements (iron and sulfur are the 1st and 5th most produced elements worldwide, respectively).
Batteries that shuttle multivalent ions such as Mg2+ and Ca2+ ions are promising candidates for achieving higher energy density than available with current Li-ion technology. Finding electrode materials that reversibly store and release these multivalent cations is considered a major challenge for enabling such multivalent battery technology. In this paper, we use recent advances in high-throughput first-principles calculations to systematically evaluate the performance of compounds with the spinel structure as multivalent intercalation cathode materials, spanning a matrix of five different intercalating ions and seven transition metal redox active cations. We estimate the insertion voltage, capacity, thermodynamic stability of charged and discharged states, as well as the intercalating ion mobility and use these properties to evaluate promising directions. Our calculations indicate that the Mn2O4 spinel phase based on Mg and Ca are feasible cathode materials. In general, we find that multivalent cathodes exhibit lower voltages compared to Li cathodes; the voltages of Ca spinels are ∼0.2 V higher than those of Mg compounds (versus their corresponding metals), and the voltages of Mg compounds are ∼1.4 V higher than Zn compounds; consequently, Ca and Mg spinels exhibit the highest energy densities amongst all the multivalent cation species. The activation barrier for the Al3+ ion migration in the Mn2O4 spinel is very high (∼1400 meV for Al3+ in the dilute limit); thus, the use of an Al based Mn spinel intercalation cathode is unlikely. Amongst the choice of transition metals, Mn-based spinel structures rank highest when balancing all the considered properties.
Dual-ion batteries (DIBs) and dual-graphite batteries (DGBs) attract increasing attention as an alternative approach for stationary energy storage due to their environmental, cost and safety benefits over other state-of-the-art battery technologies. In order to realize an extraordinary cell performance of DGBs, it is of particular importance to stabilize the interphases between electrolyte and electrode, for both the negative and positive electrodes. In this work, we present the implementation of highly concentrated electrolytes (HCEs) in DIBs and DGBs, i.e. electrolyte formulations based on either LiPF6 or LiTFSI in dimethyl carbonate (DMC), diethyl carbonate (DEC) or ethyl methyl carbonate (EMC). A reversible cycling stability of the graphitic negative electrode is proven as well as the stability of the HCEs against oxidative decomposition at the positive electrode at a cathode potential of 5V vs. Li/Li+. Additionally, we demonstrate that the anodic dissolution of the aluminum (Al) current collector is successfully suppressed by using LiTFSI-based HCEs, which show a comparable resistivity against Al dissolution as LiPF6-based electrolytes. Furthermore, a strong dependence of concentration and onset potential of anion intercalation is observed and comprehensively discussed with respect to the thermodynamic environment of the electrolyte. Overall, the use of HCEs enables a highly reversible cycling stability, providing extraordinary high specific discharge capacities of 80–100 mAh g−1 for lithium metal-based DIBs and DGBs. The evaluation of voltage efficiency (VE) and energy efficiency (EE) reveals the highest values for the EMC/LiPF6-based electrolyte, i.e. 96% (VE) and 95% (EE). In summary, the use of HCEs is a promising strategy to further optimize the electrochemical performance of DIBs and DGBs in terms of high reversible capacity and cycling stability and decreased parasitic side reactions.