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Synchrotron based in situ X-ray absorption spectroscopy (XAS) and X-ray diffraction (XRD) techniques are used to investigate changes in the electronic and local structure of LiFe0.48Mn0.48Mg0.04PO4 olivine type cathode material during charge. The Fe and Mn K-edge XANES results show that the major charge compensation is achieved by the oxidation of Fe2+ ions at lower potential plateau (∼3.5 V) and the oxidation of Mn2+ ions at higher potential plateau (∼4.1 V). In Fe K-edge EXAFS results, the increase in Fe–O peak intensity during charge indicates the decrease in the degree of structural disorder around Fe ions. Pseudo one phase reaction is observed during charge, which is consistent with the local structural behavior around Fe ions. Trace amount of Mg2+ ion decreases the lattice misfit at the phase boundary during Li extraction. The smaller lattice mismatch near the phase boundary facilitates the conversion of one phase to another resulting in less polarization and better rate capability of electrode.
Fuels based on renewable energy sources (RES) such as a variety of first and second generation biofuels as well as electricity and hydrogen from RES, are considered an important means of coping with the environmental problems of transport. The objective of this paper is to investigate the “renewable fuels” from economic, energetic and ecological perspective within a dynamic framework until 2050. The key results show that all fuels analysed have lower CO2 emissions than gasoline, but drawbacks include the high costs of hydrogen- and electricity-driven vehicles. By 2050 however these costs could be reduced due to technological learning effects and efficient policy measures (e.g. CO2-based tax). We conclude that “renewable fuels” will only play a significant role if CO2 taxes, intensified R&D and technological learning are strategically implemented.
Constructing rational structure and utilizing distinctive components are two important keys to promote the development of high performance supercapacitor. Herein, we adopt a facile two-step method to develop an in-situ heterostructure with NiCo-LDH nanowire as core and NiOOH nanosheets as shell on carbon fiber cloth. The resultant NiCo-LDH@NiOOH electrode exhibites a high specific capacitance of about 2622 F g−1 at 1 A g−1 and good cycling stability (88.5% remain after 10000 cycles). This reinforced electrochemical performance is benefit from the distinct core-shell structure, and takes advantage of the synergetic effect to supply more electrochemical active spots and pathways to accelerate electron and ion transport. Furthermore, the fabricated asymmetric supercapacitor of optimized NiCo-LDH@NiOOH//AC device displays a high energy density of 51.7 Wh kg−1 while the power density is 599 W kg−1 and presents a satisfying cycling performance.
Modifying TiO2 with nitrogen and porous N doped graphene to form mesoporous TiO2/N doped graphene nanostuctures has been successfully achieved by a two-step hydrothermal–calcining method with urea as an inhibitor and nitrogen source. Porous N doped graphene network hinders the agglomeration of TiO2 nanoparticles, and enhances the conductivity of TiO2 based electrode simultaneously, achieving the enhanced capacity and fast discharge and charge rate. As a anode material, such nanocomposite exhibits a capacity as high as 330.7 mAh g−1at a current rate of 0.5 C and a reversible capacity over 288.6 mAh g−1 accompanying a coulombic efficiency of 96.4% at a current rate of 30 C after 1000 cycles. The superior electrochemical performance is ascribed to the excellent rate performance and cycling stability, moreover, highly exciting from a fundamental point of view, the good electronic conductivity caused by N incorporated graphene sheets and the positive synergistic effect between ultrafined nanoparticles and porous N decorated graphene matrix. Additionally, the restriction to ultrasmall reaction domains with high specific surface area and mesoporous structure allowing for an almost diffusion less and nucleation-free “conversion” results in highly efficient lithium ion batteries with fast charge/discharge rate and a remarkably enhanced cycling performance.
Li-rich nickel cobalt manganese oxide (NCM) materials with partial substitution of lithium by magnesium is synthesized by the Pechini process. Different synthesized Li100-2xMgx-NCM materials (x = 0, 1, 2.5, 5, and 10) are investigated by X-ray diffraction (XRD), neutron diffraction, and scanning electron microscopy to determine the role of Mg in the structure and its impact on the morphology and electrochemical properties. The chemical composition, crystal structure, and particle morphology are compared with those of the reference (x = 0) material. Mg substitution has a significant impact on the electrochemical properties. In comparison with the reference sample, the x = 1 sample exhibits a mitigation of the voltage drop owing to more stable structure during cycling, leading to a specific discharge of 210 mAh g−1 after 100 cycles at C/10 rate. However, compositions with x ≥ 2.5 exhibit larger voltage drop in discharge, due to the faster formation of a spinel-like structure during cycling.
While air pollution levels have fallen in recent years, air quality in the United States is still poor and adversely affects the health of millions of persons. Because of physiologic changes in pregnancy, pregnant women and their fetuses are among the most vulnerable. This paper reviews the current state of our air quality, the impact that exposure to air pollution has on general health and the health of a pregnancy, and offers suggestions on how to minimize exposures.
This study thoroughly compared polyaniline (PANI)/prussian blue (PB) and PB/PANI bilayers with component films by electrochromic photographs, cyclic voltammograms, in situ transmittance spectra, in situ EQCM data and SEM pictures. It was found that both the electrochromic and redox behaviors of a PANI/PB bilayer strongly depended on which layer was deposited first. All of the experimental evidences disclosed that the inner PANI–outer PB bilayer would be superior to the inner PB–outer PANI arrangement and would display better synergistic effects, including better polyelectrochromism (colorless, light green, green/blue and deep blue) and higher redox activity and reversibility. It was also discovered by SEM that subsequent deposition of a PB film with submicron-crack openings on PANI yielded an ideal two-layer structure, but a non-idea bilayer that lacked an obvious boundary between PANI and PB layers was formed when PB was deposited first. In addition, the complex bilayer redox mechanism accompanied by a combinative K+, Cl− and H+ doping process was studied quantitatively by in situ mass flux analysis and differential transmittance–potential curves. To sum up, this work has demonstrated a simple method to prepare a polyelectrochromic bilayer and provided various useful approaches to characterize bilayer electrodes, especially for those composed of a conducting polymer and a PB analogue.
Sulfonated poly(ether ether ketone) (S-PEEK) with different degree of sulfonation (DS) has been prepared and evaluated as a proton conducting membrane for electric double layer capacitor (EDLC). The polymer electrolytes prepared with S-PEEK membrane exhibited ionic conductivities about 1.2×10−3–4.5×10−3 Scm−1 at room temperature, which depended on both soaking solvent and degree of sulfonation. The quasi-solid-state EDLCs consisted of activated carbon electrodes and S-PEEK membrane were assembled, and their electrochemical characteristics were studied by cyclic voltammetry and charge–discharge cycle tests. The effect of DS on the electrochemical performances of EDLCs has been investigated.
The electrochemical reaction mechanism of ZnO is investigated to understand its Li insertion/extraction behavior using ex situ X-ray diffraction, extended X-ray absorption fine structure, and high-resolution transmission electron microscopy. Based on these analyses, an interesting partial recombination reaction of ZnO is discovered, which demonstrates that Li2O formed during Li insertion is partially reversible. Additionally, we discover that the control of the partial recombination reaction of the metal oxide is very important for improving reversibility in the first cycle, which is a key finding for realization of highly reversible oxide-based electrode materials. In addition, to enhance the electrochemical performance of the ZnO electrode, a nanostructured ZnO/C composite is prepared by a simple high-energy mechanical milling process. This process allows the electrochemical performance of the ZnO electrode to be evaluated as an anode for rechargeable Li-ion batteries. Electrochemical tests show that the nanocomposite electrode exhibits a high initial charge capacity of 682 mAh g−1, fast rate capability of 371 mAh g−1 at 2 C, and excellent cyclability over 200 cycles.
Nanocarbon materials recognized as effective and inexpensive catalysts for independent electrochemical reactions, are anticipated to possess a broader spectrum of multifunctionality toward oxygen reduction reaction (ORR), oxygen evolution reaction (OER), and hydrogen evolution reaction (HER). A rational design of trifunctional nanocarbon catalyst requires balancing the heteroatoms-doping and defect-engineering to afford desired active centers and satisfied electric conductivity, which however is conceptually challenging while desires in-depth research both experimentally and theoretically. This work reports a N,B-codoped graphitic carbon nanocage (NB-CN) with graphitic yet defect-rich characteristic as a promising trifunctional electrocatalyst through a facile thermal pyrolysis assisted in-situ catalytic graphitization (TPCG) process. Density functional theory (DFT) calculations are conducted, for the first time, to demonstrate that the best performance for ORR/OER and HER can be originated from the configuration with B meta to a pyridinic-N, which presents a minimum theoretical overpotential of 0.34V for ORR, 0.39V for OER, and a lowest Gibbs free-energy (ΔGads) of 0.013eV for HER. A primary zinc-air battery is assembled presenting a maximum power density of 320mWcm−2 along with excellent operation durability, evidencing great potential in practical applications.
In the development of lithium ion batteries for electric vehicle applications, much effort has been made in fabrication and optimization of active materials. Mechanical properties of the electrode laminate, which are also very critical determining the durability of the cell, have long been ignored. In this study, graphite laminates of the same chemical composition are prepared by using different mixing technologies. With similar breaking strength, Young’s modulus of the laminate is found to be very different according to the mixing order. Electrochemical performances of the graphite laminates are investigated against Li anode and Li[Ni1/3Co1/3Mn1/3]O2 cathode, respectively. Long-term cycling performance is closely related with the Young’s modulus of the graphite laminate. Whereas the laminates of low modulus cycles well during the investigated 600 deep charge–discharge cycles, the electrodes of high modulus fail at around 350 cycles. Electrochemical degradation mechanism for the laminate of high modulus is associated with the significant impedance rise aroused from mechanical failure. After the long-term cycling test, lots of cracks are observed on the high modulus electrode along the particle boundaries while the mechanical integrity of the low modulus laminate is well maintained.
Our aim was to ascertain whether releasing the medial head of he gastrocnemius improves clinical and functional outcomes of sedentary patients with long-standing tendinopathy of the main body of the Achilles tendon and allows return to daily activities.
When marking the subjective midpoint of a horizontal line, patients with left unilateral neglect typically deviate rightward. Different accounts of this pattern of performance refer either to a biased competition between the two hemi-segments of the line, with the right part being subjectively perceived as longer than the left part, or to a distortion of a cognitive representation of space, with spatial coordinates progressively relaxing from the right to the left. These accounts make different predictions about the role of the right part of the line, which is crucial in the biased competition account, but less important in the distortion account. To test these predictions, we asked participants to set the endpoints and the centre of perceived and imaginary lines. Contrary to previous studies, we controlled for the direction of performance of the endpoint task, with left-to-right trials and right-to-left trials being performed in separate blocks. Five patients with right-hemisphere lesions and left neglect demonstrated the typical asymmetries when a right-sided stimulus (segment or endpoint) was present, but showed either normal performance or a reversed (leftward) bias while setting the endpoints and the centre of an imaginary line starting from the left side, when no right-sided visual stimulus was present until completion of each trial. We concluded that the right-sided portion of the line has a crucial importance in determining patients' rightward deviations in line bisection, consistent with the biased competition hypothesis and with neurocognitive models of attentional orienting.
Modelling the dynamics of multi-component alloy systems under extreme conditions and predicting the resulting compositions is a complex task. Here, the authors develop a theoretical framework to predict vaporisation and condensation in multi-component flows during electron beam welding and demonstrate how these processes lead to chemical heterogenisation.
Phenomena at electrode/electrolyte interface of LiNi0.5Mn1.5O4 are studied by in situ total-reflection fluorescence X-ray absorption spectroscopy (TRF-XAS), ex situ X-ray photoelectron spectroscopy (XPS), and electrochemical tests. Flat and well-defined thin films of LiNi0.5Mn1.5O4 prepared by pulsed laser deposition (PLD) are used as model electrodes to facilitate the observation of the interface. The thin-film LiNi0.5Mn1.5O4 electrode showed good cycling characteristics at around 4.7 V vs. Li/Li+. The TRF-XAS measurements reveal that nickel and manganese species at the surface have almost the same chemical states and local environments as those in the bulk when in contact with organic electrolyte solutions (1 mol dm−3 LiClO4 in a 1:1 volumetric mixture of ethylene carbonate and diethyl carbonate). This is in sharp contrast to the behavior of a LiCoO2 electrode, in which the surface cobalt species is irreversibly reduced by soaking to the organic electrolyte solutions, leading to gradual material deterioration during the delithiation/lithiation cycling (D. Takamatsu et al., Angew. Chem. Int. Edit., 51 (2012) 11597). It is suggested that the electrolyte decomposition products detected by XPS form a protective layer to restrict the reduction of the surface species of LiNi0.5Mn1.5O4, leading to good cycling characteristics of LiNi0.5Mn1.5O4 in spite of its high operating potential.
This work provides an overview of available methods and algorithms for on-board capacity estimation of lithium-ion batteries. An accurate state estimation for battery management systems in electric vehicles and hybrid electric vehicles is becoming more essential due to the increasing attention paid to safety and lifetime issues. Different approaches for the estimation of State-of-Charge, State-of-Health and State-of-Function are discussed and analyzed by many authors and researchers in the past. On-board estimation of capacity in large lithium-ion battery packs is definitely one of the most crucial challenges of battery monitoring in the aforementioned vehicles. This is mostly due to high dynamic operation and conditions far from those used in laboratory environments as well as the large variation in aging behavior of each cell in the battery pack. Accurate capacity estimation allows an accurate driving range prediction and accurate calculation of a battery's maximum energy storage capability in a vehicle. At the same time it acts as an indicator for battery State-of-Health and Remaining Useful Lifetime estimation.
The hybrid films composed of single-walled carbon nanotube (SWNT) macro-films and α-Fe2O3 nanoparticles in fine crystalline size (6–20 nm) are prepared by a simple heat treatment of the as-synthesized SWNT macro-films. The SWNT macro-films with superior conductivity and flexibility can facilitate the charge transfer processes as well as accommodate the volumetric change of the α-Fe2O3 nanoparticles due to the Li-intercalated phase transformations, enabling high specific capacities over 1000 mAh g−1 and an excellent cyclic stability up to 100 cycles for the α-Fe2O3/SWNT hybrid films. The increment of the capacity to approach the theoretical capacity of α-Fe2O3 during cycling results from the relaxed conversional reactions between the reduced and oxidized states of iron ions (Fe0, Fe(II) and Fe(III)). Experimental results have shown that the thickness of the hybrid films has a significant impact on the diffusion coefficient of Li+. With a thickness comparable to Li+ characteristic diffusion length in the range of 300–500 nm, the hybrid films exhibit an optimal electrochemical performance. The findings on the synthesis approach and the thickness effect provide a promising strategy for a large-scale production of high-performance anode materials for Li-ion batteries.
In this study, the heat generation and dissipation terms are classified for both irreversible and reversible heat. The irreversible heat is formulated according to the Joule-heating model with internal resistance in order to circumvent the calculation of electrochemical reactions that require significant computational loads. The internal resistance in the Joule-heating model is determined via electrochemical impedance spectroscopy (EIS). The EIS tests are conducted with state-of-charge (SOC) increments of 5%. To capture rapid changes in the internal resistance, the EIS tests are conducted with smaller intervals in the 0–10% and 90–100% SOC regions. Additionally, an analytical formulation of the resistance is derived from the electrochemical kinetic equations to explain the rapid changes. Analysis reveals that the rapid changes are due to the Li intercalation phenomenon in the electrodes. Thermal analyses are conducted according to the proposed model for Li-ion single cells, and the simulation results exhibits good agreement with the experimental data. Finally, a thermal analysis for a full-scale battery tray comprising 280 cylindrical cells is performed, and the applicability of the proposed model is confirmed by comparing the simulation results with the experimental findings.
Despite its high reversibility for Li+ intercalation, graphite is known to be electrochemically inactive for Na+ intercalation. On the contrary, recent studies have demonstrated that graphite is active and shows excellent rate and cycle performance for Na+-solvent cointercalation but it exhibits poor performance for Li+-solvent cointercalation. Herein, we elucidate the mechanism of Li+- and Na+-solvent cointercalation into graphite and the origin of the strikingly different electrochemical performance of Li+- and Na+-solvent cointercalation cells. Na+ intercalation into graphite is thermodynamically unfavorable, but Na+-diglyme cointercalation is very favorable. The diglyme–graphene van der Waals interaction reinforces the interlayer coupling strength and thereby improves the resistance of graphite to exfoliation. The transport of solvated Na ions is so fast that the diffusivity of Na+-diglyme complexes is markedly faster (by five orders of magnitude) than that of Li+-diglyme complexes. The very fast Na+-diglyme conductivity is attributed to facile sliding of flat diglyme molecules, which completely solvate Na ions in the interlayer space of graphite. The slow Li+-diglyme conductivity is ascribed to steric hindrance to codiffusion caused by bent diglyme molecules that incompletely solvate Li ions. The bent and flat diglyme molecules surrounding Li and Na ions, respectively, are highly associated with the strong Li+–graphene and weak Na+–graphene interactions, respectively.
This research work focuses on evaluating the effect of battery state of charge (SOC) in the fuel consumption and gaseous pollutant emissions of a Toyota Prius Full Hybrid Electric Vehicle, using the Vehicle Specific Power Methodology. Information on SOC, speed and engine management was obtained from the OBD interface, with additional data collected from a 5 gas analyzer and GPS receiver with barometric altimeter. Compared with average results, 40–50% battery SOC presented higher fuel consumption (57%), as well as higher CO2 (56%), CO (27%) and NO x (55.6%) emissions. For battery SOC between 50 and 60%, fuel consumption and CO2 were 9.7% higher, CO was 1.6% lower and NO x was 20.7% lower than average. For battery SOC between 60 and 70%, fuel consumption was 3.4% lower, CO2 was 3.6% lower, CO was 6.9% higher and NO x was 24.4% higher than average. For battery SOC between 70 and 80%, fuel consumption was 39.9% lower, CO2 was 38% lower, CO was 33.9% lower and NO x was 61.4% lower than average. The effect of engine OFF periods was analyzed for CO and NO x emissions. For OFF periods higher than 30 s, increases of 63% and 73% respectively were observed.
LiFePO4/C of high purity grade was successfully synthesized by microwave accelerated sol–gel synthesis and showed excellent electrochemical performance in terms of specific capacity and stability. This cathode material was characterized in battery configuration with a graphite counter electrode by USABC–DOE tests for power-assist hybrid electric vehicle. It yielded a non-conventional Ragone plot that represents complexity of battery functioning in power-assist HEV and shows that the pulse power capability and available energy of such a battery surpasses the DOE goal for such an application.
Nanosheet-like structures of copper cobaltite (CuO/Co2O4) decorated on N-MWCNT electrodes were synthesized through hydrothermal process in the presence of ammonia/urea. The structural and morphological properties were characterized by Raman, XRD, XPS, SEM, SEM-EDX and FE-TEM analysis. The electrochemical properties of the CuO/Co2O4@N-MWCNT hybrid electrodes were studied using cyclic voltammetry, galvanostatic charge−discharge, and electrochemical impedance analyses. The prepared CuO/Co2O4@N-MWCNT and CuO@N-MWCNT electrodes showed a specific capacitance of ∼246 F g−1 and 100 F g−1 at a current density of 0.5 A g−1 for three electrode assembly. Further, the asymmetric cells also fabricated and it delivered the highest specific capacitance of 268 F g−1 and 279 F g−1 for CuO@N-MWCNT and CuO/Co2O4@N-MWCNT electrodes respectively. These electrodes possessed very good capacitance behavior with 89% retention even after 5000 cycles at 0.5 A g−1 which overlay a way to use as promising candidates for the high-performance supercapacitors.
Absolute methanol extract leaf of Costus afer was comprehensively investigated for free radical scavenging activities and antioxidant activities using battery of testing: 1, 1-diphenyl-2-picrylhydrazyl (DPPH) scavenging, hydroxyl radical scavenging, hydrogen peroxide radical scavenging, 2, 2′-azino-bis (3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) scavenging, nitric oxide inhibition, anti-lipid peroxidation, ferrous chelating potential, reducing power potential, total antioxidant capacity, cupric reducing antioxidant capacity CUPRAC and ferric reducing antioxidant power (FRAP). The content of phenol, flavonoid, cupric, anthocyanin were also investigated. The results suggest that the antioxidant potentials of the extract may be responsible for its medicinal potentials. Cell viability assay revealed that up to12 μg/ml of the extract is safe for Chang liver cell and no sign of toxicity was observed after the extract treatment of 2000 mg/kg in albino rats.