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Prussian Blue Analogues (PBAs) with general formula Na x MA[MB(CN)6] y ·z H2O (MA, MB =transition metal) are promising low cost, high rate and high capacity cathodes for sodium ion battery (SIB) technology. Here, we have studied the PBA Na1.32Mn[Fe(CN)6]0.83·z H2O (z =3.0 and 2.2) with varying structural modifications (monoclinic and cubic) using in operando quasi-simultaneous X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS). We observed a series of reversible structural phase transitions which accompany Na insertion/extraction during electrochemical cycling. The samples show pronounced differences in their galvanostatic charge and discharge profiles which could be linked to structural and electronic response. Different desodiation and sodiation mechanisms were identified. The influence of [Fe(CN)6] vacancies and water content on the electrochemical performance was investigated.
Structural degradation and side reaction in cathode materials have been regarded as the main issues that compromise the capacity and cycle stability of Ni-rich LiNi0.8Co0.15Al0.05O2. Herein, an inside-out modification method was reported to stabilize internal structure and restrain side reactions of LiNi0.8Co0.15Al0.05O2, composing of doping Mg inside the layer structure and coating Al2O3 outside the cathode materials particles. Through dual protection strategies, an unprecedented capacity retention as high as 99% after 100cycles and 95% after 250cycles (from 178 to 168.9mAhg−1) was achieved at 1.0C, which are much more superior among LiNi0.8Co0.15Al0.05O2 cathodes using previously reported modification methods. X-ray diffraction results indicated that Al and Mg ions were successfully introduced into the bulk materials and exhibited excellent hexagonal structure. This work highlights that the multiple modified method is a promising strategy to enhance the cycling performance of LiNi0.8Co0.15Al0.05O2, and these enhancements can be attributed to the protection from “inside” to “outside” of LiNi0.8Co0.15Al0.05O2 particles, which suppress phase transition and cation mixing inside the materials, and reduce side effects outside the particles, thus allows for rapid electron transport during the electrochemical Li+ insertion/extraction reaction.
Silicon has been regarded as one of the most promising alternatives to the current commercial graphite anode for Li-ion batteries due to its high theoretical capacity and abundance. Although high gravimetric capacity (mAh/g) of Si-based materials can be achieved, areal capacity (mAh/cm2), an indication of the energy stored at the electrode level, has rarely been discussed. Herein, a novel micro-sized graphene/Si–C composite (G/Si–C) is reported, in which micro-sized Si–C particles are wrapped by graphene sheets. Owing to dual conductive networks both within single particles formed by carbon and between different particles formed by graphene, low electrical resistance can be maintained at high mass loading, which enables a high degree of material utilization. Areal capacity thus increases almost linearly with mass loading. As a result, G/Si–C exhibits a high areal capacity of 3.2mAh/cm2 after 100 cycles with high coulombic efficiency (average 99.51% from 2nd to 100th cycle), comparable to that of commercial anodes. The current findings demonstrate the importance of building a conductive network at the electrode level to ensure high material utilization at high mass loading and may shed light on future designs of Si-based anodes with high areal capacity.
Structural changes in the surface of edge plane highly oriented pyrolytic graphite (HOPG) electrodes were studied in ethylene carbonate (EC)-based electrolytes by in situ Raman spectroscopy. The Raman spectra revealed that the surface crystallinity of graphite was significantly lowered by the initial intercalation and de-intercalation reactions of Li+. This structural degradation resulted in a sluggish stage transition of Li-GIC in the vicinity of the edge plane in the subsequent potential cycle. On the other hand, when the film-forming additive vinylene carbonate was used in the EC-based electrolyte solution, the crystallinity of the edge plane HOPG was maintained even after potential cycling. In addition, the phase transition of Li-GIC during the 2nd potential cycle proceeded in the same manner as in the initial cycle. Based on the present results, we discuss the suppressive role of film-forming additives on the degradation of the surface structure as it relates to the intercalation mechanism of Li+.
A prediction-based power management strategy is proposed for fuel cell/battery plug-in hybrid vehicles with the goal of improving overall system operating efficiency. The main feature of the proposed strategy is that, if the total amount of energy required to complete a particular drive cycle can be reliably predicted, then the energy stored in the onboard electrical storage system can be depleted in an optimal manner that permits the fuel cell to operate in its most efficient regime. The strategy has been implemented in a vehicle power-train simulator called LFM which was developed in MATLAB/SIMULINK software and its effectiveness was evaluated by comparing it with a conventional control strategy. The proposed strategy is shown to provide significant improvement in average fuel cell system efficiency while reducing hydrogen consumption. It has been demonstrated with the LFM simulation that the prediction-based power management strategy can maintain a stable power request to the fuel cell thereby improving fuel cell durability, and that the battery is depleted to the desired state-of-charge at the end of the drive cycle. A sensitivity analysis has also been conducted to study the effects of inaccurate predictions of the remaining portion of the drive cycle on hydrogen consumption and the final battery state-of-charge. Finally, the advantages of the proposed control strategy over the conventional strategy have been validated through implementation in the University of Delaware's fuel cell hybrid bus with operational data acquired from onboard sensors.
We report herein on extensive post-mortem analysis of rechargeable Li-ion batteries after prolonged cycling at 25 and 40°C. The 18650-type batteries produced by standard procedure at LG Chem. Inc. were comprised of graphitic carbon anodes, LiCoO2 cathodes, and a commercial, Li-battery grade ethylene carbonate, ethyl–methyl carbonate (EC-EMC)/LiPF6 solution. The batteries were dismantled under highly pure inert atmosphere after prolonged cycling by a specially designed system, followed by analysis of both electrodes by SEM, XRD, FTIR, and electrochemical methods (voltammetry, impedance spectroscopy). The residual solution was analyzed by gas chromatography–high-resolution mass spectrometry (GCMS), and by Karl Fischer titration (for trace H2O content). It was found that the structure of both electrodes is basically retained during prolonged cycling. However, they developed surface films that considerably increase their impedance, thus badly affecting the battery performance after a few hundred charge–discharge cycles. It also appears that part of the cathode's active mass became electronically isolated from the current collector. Hence, the impedance of both electrodes increases considerably upon cycling. The residual solutions contained 10–15 times more water than the pristine solution, as well as products of trans-esterification of the alkyl carbonates, and some fluorinated and phosphorous-containing organic species. The surface chemistry of both electrodes seems to be dominated primarily by LiF formation. Capacity fading mechanisms of Li-ion batteries are discussed.
Porous carbon materials, such as activated carbon and activated carbon aerogel, were modified chemically by using a surfactant sodium oleate to improve their specific capacity for high-rate electrochemical double layer capacitors (EDLCs) application. Main impacting factors have been examined for surface modification of activated carbon. Specific capacity can be improved significantly by the surface modification. The enhancement in specific capacity is mainly attributable to improvement in wettability of carbon materials, resulting in a higher usable surface area and a smaller internal resistance. The effects from surface modification become more marked at higher discharge rates, and a much higher energy density can be achieved for the modified carbon materials. In addition, the modified carbon materials possess comparable cycle stability to the original carbon.
Tin-based (Sn) metal anode has been considered an attractive candidate for rechargeable lithium batteries due to its high specific capacity, safety and low cost. However, the large volume change of Sn during cycling leads to rapid capacity decay. To address this issue, Sn foil was used as a high capacity anode by controlling the degree of lithium uptake. We studied the electrochemical behavior of Sn foil anode in half cell and full cell with sulfur cathode, including phase transform, morphological change, discharge/charge profiles and cycling performance. Enhanced cycling performance has been achieved by limiting the lithiation capacity of the Sn foil electrode. A full cell consisting of a pre-lithiated Sn foil anode and a sulfur cathode was constructed and tested. The full cell exhibits an initial capacity of 1142 mAh g−1 (based on the sulfur mass in the cathode), followed by stable cycling performance with a capacity retention of 550 mAh g−1 after 100 cycles at C/2 rate. This study reports a potential prospect to utilize Sn and S as a combination in rechargeable lithium batteries.
The data for formaldehyde and acetaldehyde levels in ambient air of the city of Rio de Janeiro, obtained in the period from 4 December 1998 to 17 January 2001 is presented. A total of 28 samples were collected at a downtown area, where emissions may be mainly attributed to the vehicular fleet. Values between 1.52 and 54.31ppb for formaldehyde and between 2.36 and 45.60ppb for acetaldehyde were obtained. The high acetaldehyde/formaldehyde ratios (0.76 to 1.61) are a consequence of the use of oxygenated fuels. Brazilian cities are unique in that the vehicles use hydrated ethanol (over 4 million of light duty vehicles), gasohol (a mixture with gasoline and 24% v/v of ethanol) and diesel fuels. The analysis of vehicle exhaust and model simulations of the air quality in August and December 1999, confirmed that the high levels of acetaldehyde could be attributed to direct emissions of the vehicular fleet and to the photochemical initiated oxidation of organic compounds.
Layered LiMn1−x M x O2 (M=Zn or Fe) (0≤ x ≤0.3) samples are synthesized from the corresponding sodium analogues by an ion-exchange method using LiBr in n-hexanol at 160°C. The samples are subjected to physicochemical and electrochemical characterization. X-ray diffraction data indicate the formation of layered structures for the LiMn1−x Zn x O2 samples up to x =0.3 and for LiMn1−x Fe x O2 samples up to x =0.2. Among these, LiMn0.95Zn0.05O2 and LiMn0.95Fe0.05O2 provide the highest capacity values of 180 and 193mAhg−1, respectively. Both Zn- and Fe-substituted samples display good capacity retention up to 30 charge–discharge cycles. Electrochemical impedance spectroscopy and galvanostatic intermittent titration data corroborate the results obtained from cyclic volatmmetry and charge–discharge cycling.
The freeze-drying method is proposed as an effective synthesis process for the obtaining of LiFePO4/C composites. The citric acid is used as a complexing agent and carbon source. After the low temperature annealing, the freeze-dried solution leads to a homogeneous carbon covered LiFePO4 sample. The chemical characterization of the material included ICP and elemental analysis, infrared spectroscopy, X-ray diffraction, magnetic measurements and thermal analysis. SEM and TEM microscopies indicate an aggregate morphology with tiny particles of lithium iron phosphate inside a carbon matrix. Impedance spectroscopy showed a 8.0×10−7 Scm−1 conductivity value. Cyclic voltammetry graphics displayed the two peaks corresponding to the Fe(II)/Fe(III) reaction and demonstrated the good reversibility of the material. The specific capacity value obtained at C/40 rate was 164mAhg−1, with a slight decrease on greater C-rates reaching 146mAhg−1 at C/1. The capacity retention study has evidenced good properties, with retention over 97% of the maximum values in the first 50 cycles, which allows an effective performance of the freeze-dried sample as cathodic material in lithium-ion batteries.
A facile sacrificial-template method combined with a post annealing treatment was developed to synthesize uniform hollow polyhedral (cubic, octahedral and dodecahedral) NiO materials. The electrochemical and lithium-ion battery performances of the shape controlled hollow polyhedral NiO materials were examined, providing us with a description of the structure-performance correlations of hollow polyhedral anodes. The lithium-ion battery performance was found to be highly dependent on the hollow polyhedral NiO morphology. The hollow dodecahedral NiO (HD-NiO) electrode exhibited excellent cycling stability, high reversible capacity and good rate capacity compared to the other two NiO samples. At a current density of 0.1Ag−1, the hollow dodecahedral NiO electrode displayed an especially high capacity of 980mAhg−1 after 100 cycles, which was much higher than that of the hollow cubic and octahedral NiO electrodes. Most important of all, when assembled with LiCoO2 to construct a full lithium-ion battery (HD-NiO//LiCoO2), the HD-NiO electrode exhibited a reversible capacity of 627mAhg−1 at a current density of 0.1Ag−1 in the potential range of 1.0–3.8V. These results clearly demonstrate that hollow polyhedral NiO has potential as an anode material in next generation lithium-ion battery systems with improved storage capacities.
This short communication investigates whether or not US coal consumption follows a stationary process by examining coal consumption for the 50 US states over the period 1982–2007. Employing several panel unit root and stationarity tests with endogenously determined structural breaks, the results indicate that coal consumption is integrated of order zero. Thus, energy conservation policies oriented towards the reduction of coal consumption will only have short-term effects.
Long chain protonic acid (dodecylhydrogen sulfate-DHS) along with small molecule acid (sulfuric acid-H2SO4) was introduced as dopants in polyaniline salt (PANI–H2SO4–DHS), hereafter referred as PANI, via aqueous/emulsion polymerization pathway of aniline. Polyaniline salt–acetylene black composites (PANI–AB) were prepared in one-step via aqueous/emulsion polymerization pathway using various amounts of acetylene black (AB). Formation of PANI and PANI–AB was confirmed from infrared and X-ray diffraction patterns. The highest conductivity obtained for PANI–AB composite was 6.2Scm−1, which is slightly higher than that of PANI (1.3Scm−1). PANI prepared by aqueous polymerization pathway showed nano fibres with diameter of 10–30nm. Use of 5wt% of AB with respect to the amount of aniline used in the polymerization reaction of aniline, PANI–AB showed spheres covered nano fibres with high porosity. By increasing the amount of AB to 10wt%, nano fibres are getting closure, which reduced the porosity. Further increase in the amount of AB to 15wt%, nano fibres disappear. PANI and PANI–AB were used as electrode materials in symmetric supercapacitor cell. Specific capacitance, Energy and power densities of PANI–AB composite were found to be 157.6Fg−1., 15.7Whkg−1 and 600Wkg−1 respectively.
Surface-nanostructured TiO2 nanorods were synthesized hydrothermally at 180 °C. Such nanorods have ‘crack-like’ surfaces that resemble burnt charcoal. Compared to nanorods with relatively smoother surfaces, the charcoal-like nanorods have higher-specific surface areas. By using the nanorods as a light-scattering layer in double-layered dye-sensitized solar cells, the cells based on the charcoal-like nanorods have 20 % higher dye loading and also higher diffuse reflectance compared with cells utilizing ‘smooth’ nanorods. The efficiency of a screen-printed double-layer dye-sensitized solar cell based on the charcoal-like nanorods is higher at 7.29 %. Electrochemical impedance spectroscopy was also carried out to understand the charge transfer process better.
The aim of this study is to explore the concurrent validity of the Behavioral Inhibition Scale 3-6 (BIS 3-6), a scale created for the early detection of the temperamental disposition toward social anxiety. Seventy-three participants were randomly selected from a wide sample of preschool-age children to undergo systematic observation using the Behavioral Inhibition Paradigm. Parents and teachers rated the BIS 3-6. Clinicians and researchers also measured behavioral inhibition. The BIS 3-6 scores correlate between r = 0.2 and r = 0.6 with the observational indicators, and all correlations are in the expected direction. A discriminant analysis supports a good capability of the BIS 3-6 scores to identify extreme inhibition. Consistent with previous research and given the discrepancy among parent and teacher reports and observational measures, the moderate convergence among the BIS 3-6 trait-measurements and the observational state-measurements support the validity of the BIS 3-6 scores. This study advances the validation process for a new tool intended to early detect impairing behavioral inhibition.
Since the late 1960s, India has accumulated major ground systems capabilities in its space program. This article discusses the process of building competence and technological learning, with a specific focus on the role of international collaboration, foreign imports, and indigenous efforts during the technology acquisition and building of rocket launching systems, satellite control and tracking systems, and earth stations. It highlights the importance of foreign technology inputs, particularly in the formative phase, where they are extremely helpful for building competence in developing countries like India. It demonstrates that strong indigenous efforts, combined with foreign imports, were vital in helping India achieve threshold capability and sustain technological change in the accumulative phase. It illustrates that foreign imports and indigenous efforts played complementary roles in building competence in India's ground systems technology.
Here, we investigate the feasibility of using a liquid plasma spray process as a novel method for the cost-effective fabrication of a nanonetwork of La0.4Sr0.6Co0.2Fe0.8O3−δ (LSCF) and Ce0.8Gd0.2O2−δ (GDC) composite as a high-performance cathode for intermediate-temperature solid oxide fuel cells. A suspension containing well-dispersed nanosized GDC particles in an LSCF precursor solution is designed as the feedstock. The effects of GDC concentration in the suspension on the phase composition, microstructure, and electrochemical performance of the resulting cathode are studied. When the GDC concentration increases to 15 g L−1, the nanosized GDC particles distribute uniformly and continuously on the LSCF backbone to form a porous network structure. The electrochemical studies further indicate that the cathode polarization decreased with the increase in GDC concentration from 0 g L−1 to 15 g L−1, whereas a further increase in the GDC concentration increases the cathode polarization instead. At 600 and 750 °C, the cathode prepared using 15 g L−1 GDC concentration exhibits an impressive area-specific polarization resistance (Rp) of 0.1 Ω cm2 and 0.009 Ω cm2, respectively. Finally, the Rp of the optimal cathode almost does not change after the isothermal dwelling at 650 °C for 350 h.
Publisher Summary Safety is a management responsibility requiring an awareness of all relevant local legislations and strategies. Plants must be properly designed, installed, commissioned, operated and maintained. Depending upon the risk, working procedures should be documented, for example, as codes of practice. Operation includes normal start-up, normal and emergency shutdown, and most activities performed by the production team. While inherently safe plant design limits inventories of hazardous substances, inherently safe operation ensures that the number of individuals at risk is minimized. Access to the plant for non-essential operational people, such as maintenance engineers, post staff, administrators, quality control samplers, warehouse staff delivering raw material or plant items or collecting finished product, members of security, visitors etc., must be controlled. Safe handling of chemicals demands a combination of hardware and software such as operating procedures, staff selection and training.
Porous nickel oxide films are directly deposited onto conducting indium tin oxide coated glass substrates by cyclic voltammetric (CV), galvanostatic, and potentiostatic strategies in a plating bath of sodium acetate, nickel sulfate, and sodium sulfate. By tuning the deposition parameters, it is possible to prepare nickel oxide films with various morphologies and structures. Film formation relies on the oxidation of dissolved Ni2+ to Ni3+, which further reacts with the available hydroxide ions from a slightly alkaline electrolyte to form insoluble nickel oxide/hydroxide deposits on the substrate. A compact film with particularly small pores is obtained by CV deposition in a potential range of 0.7–1.1V. A galvanostatically deposited film is structurally denser near the surface of the substrate, and becomes less dense further away from the surface. Interestingly, a potentiostatically deposited film has pores distributed uniformly throughout the entire film. Therefore, for obtaining a uniform film with suitable pore size for electrolyte penetration, potentiostatic deposition technique is suggested. In addition, except for CV deposition, the deposited films resemble closely to cubic NiO when the annealing temperature exceeds 200°C.
Climate and energy targets, as well as decreasing costs have been leading to a growing utilization of solar photovoltaic generation in residential buildings. However, even in buildings with the same level of yearly generation and consumption the mismatch between the demand and photovoltaic generation profiles leads to large power flows between the household and the grid. Such situation creates problems to the electrical grid management and can be a source of economic losses to the end-user. This paper presents an energy storage system designed in the context of residential buildings with photovoltaic generation. The objective of such system is to increase the matching between the local generation and consumption, as well as to decease the energy bill, using lithium-ion batteries as a storage device. Such system was modelled and simulated using real data of solar radiation and energy consumption from a typical residential household in Coimbra (Portugal). The results show that the designed system was able to reduce the energy sent to and consumed from the grid in 76% and in 78.3%, respectively, as well as the energy bill in 87.2%.
A considerable number of post-bariatric surgery patients report problematic eating behaviors (PEBs) and/or eating disorders (EDs). Examining psychosocial variables associated with ED symptoms may identify targets for postoperative interventions to reduce these behaviors and improve surgical outcomes.