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This study determined the potential range where the dissolution of a surface film on a thin film LiMn2O4 electrode, which forms during electrode synthesis, and the formation of a new surface film during cycling at room temperature using an in situ bending beam method (BBM) and an in situ electrochemical quartz crystal microbalance (EQCM) technique with cyclic voltammetry and a galvanostatic charge/discharge cycle. The electrolytes used were LiClO4/EC-DEC, LiClO4/PC and LiPF6/EC-DMC. The deflectogram and massogram showed large peaks during the anodic scan only in the first cycle. These phenomena, were observed regardless of the electrolytes and scan rate used. The tensile strain and the mass reduction in the early stage of the strain peak and the mass peak are related to the dissolution of the initial surface film. In addition, the compressive strain and the mass increase are related to the formation of a new surface film during cycling. The potential ranges where the formation of the new surface film begins ranged from 4.03 to 4.1V, which appears to terminate at the end of the first anodic scan, and was also observed during the galvanostatic charge/discharge cycle in the same potential range.
The design, fabrication, and performance characterization of a micro-tubular solid oxide fuel cell (SOFC) are presented. The cell has a yttri stabilized zirconia (YSZ), electrolyte, a nickel/YSZ cermet anode, and a lanthanum strontium manganate (LSM) cathode. The cathode compartment is supplied with atmospheric air, and the anode compartment fueled with hydrogen at a constant rate of 20 ml/min. The cell is operated for more than two hours at a constant voltage of 0.5 V at a temperature of 800°C. The operation of the cell through several thermal cycles is steady and the rate of degradation cell is low.
A facile one-step solvothermal method has been put forward to construct Ni3Sn2@reduced graphene oxide (Ni3Sn2@rGO) composite. The Ni3Sn2 alloys in the composite with regular quasi-spherical morphology and an average size of 216nm are homogeneously encapsulated into rGO sheets. As a promising anode material for lithium-ion batteries (LIBs), the as-prepared Ni3Sn2@rGO composite exhibits a high initial discharge capacity of 1315mAhg−1 and reversible capacity of 554mAhg−1 after 200 cycles at a current density of 100mAg−1. Even at a high current density of 800mAg−1, a substantial discharge capacity of 422mAhg−1 is delivered. The excellent cycling stability and remarkable rate capability of the designed Ni3Sn2@rGO composite can be attributed to the synergistic effects between Ni3Sn2 alloy and rGO matrix, and the rational cooperative advantage of the ball-like alloy morphology and the buffering effects of the inert nickel matrix as well as the flexible rGO matrix.
A commercial rice paper (RP) is used for the first time as a separator membrane in lithium-ion batteries. It consists of interpenetrating cellulose fibers with a diameter of about 5–40μm to form a highly porous structure. The RP is found to be electrochemically stable at a potential below 4.5V vs. Li+/Li. Several kinds of electrode materials including graphite, LiFePO4, LiCoO2 and LiMn2O4 are used to test the compatibility of the RP in Li-ion batteries and to compare with a commercial polypropylene/polyethylene/polypropylene separator membrane. The RP separator with the same thickness gives rise to a lower resistance than the commercial separator. Due to the wonderful flexibility, high porosity, low cost and excellent electrochemical performance of the RP membrane, it is promising to partially replace commercial separators in lithium-ion batteries for low power applications.
Suicidal thoughts and behaviors are a significant health concern for adolescents. Extant research suggests that sexual and gender minority adolescents are a vulnerable population at elevated risk for suicidal thoughts and behaviors, yet to date few studies have examined the unique associations between adolescent gender nonconformity and suicide risk. This study examined data from the Youth Risk Behavior Surveillance Survey (n = 7730) to estimate the association between gender nonconformity and high school-aged adolescents’ likelihood of endorsing four distinct suicide outcomes: suicidal ideation, suicide plans, any suicide attempts, and single vs. multiple suicide attempts. Multivariate logistic regression analyses were utilized to control for other known risk factors for suicidal thoughts and behaviors, including age, sex, sexual minority status, depression symptoms, and suicidal ideation. Results revealed that gender nonconformity was significantly associated with higher odds of reporting suicidal ideation, suicide plans, and multiple suicide attempts in the past year above and beyond other known risk factors. Gender nonconformity is an understudied vulnerability factor that should be taken into consideration by researchers and clinicians seeking to understand adolescents’ risk for suicidal thoughts and behaviors.
A facile strategy is developed for the synthesis of hierarchical polyaniline nanowires/ordered bimodal mesoporous carbon (PANI/OBMC) composites via chemical oxidative polymerization. Structural and morphological characterizations indicate that the polyaniline nanowire arrays with 20–30 nm diameters are grown on the surface of the OBMC. The bimodal pore distribution and hierarchical nanostructure endow the PANI/OBMC composite with high surface area of 599 m2 g−1. Electrochemical performance of the hierarchical PANI/OBMC composite as supercapacitor electrode materials has been evaluated by cyclic voltammetry and galvanostatic charge–discharge techniques. The hierarchical composite with 60 wt% PANI possesses the highest specific capacitance of 517 F g−1 and outstanding cycling stability with a capacitance retention of 91.5% after 1000 cycles. The coexistence of primary mesopores and abundant small mesopores is in favor of the fast penetration of electrolyte and the unique hierarchical structure facilitates the ion diffusion and shortens the charge transfer distance, which lead to superior electrochemical performance of PANI/OBMC-60%.
We report a novel and versatile method of grafting polymers onto lithium titanium oxide (LTO) by dispersion-mediated interfacial polymerization. A myriad of polymers can be grafted by this method, and the hybrid-polymer particles are compatible with all kinds of binders used in lithium-ion batteries. This method is capable of producing thin and homogenous polymer films that are useful for battery applications. A coating of poly(styrene) effectively prevents degradation of the cell after float test without affecting performance at high C rates.
Due to the flexibility and excellent electrochemical properties, carbon nanofibers have been proposed as promising anode material for lithium ion batteries. In this paper, through in-situ reduction of C/CuO/rGO after electrospinning to form abundant active sites at carbon nanofibers, a novel C/Cu/rGO anode is prepared. The C/Cu/rGO anode owns a capacity of ∼400 mAh/g at 1 A/g after 600 cycles, a value well above those of C and C/rGO (<200 mAh/g). Cu nanoparticles greatly improve the lithium storage performance by forming defects as active sites for ion storage and owning a pseudo capacitance due the interrupted ordered atomic arrangement and the increase of surface desaturation in the anode. Synergistically, rGO improves the conductivity and stability. This work provides an efficient anode materials platform towards high-capacity and flexible lithium ion batteries.
Crystalline α-Fe2O3 powder was prepared by the mechanical milling of crystalline α-FeOOH at room temperature in air. This result means that crystalline α-FeOOH is dehydrated by mechanical milling at room temperature. The obtained α-Fe2O3 powder worked as a rechargeable electrode material in lithium ion conductive organic electrolytes. The electrodes exhibited high discharge capacities of over 1000mAhg−1 corresponding to 6 Li per α-Fe2O3 at potentials ranging from the open circuit potential to 0.5V (versus Li+/Li) in the first discharging (lithium insertion) process. This suggests that the valence deviation from Fe3+ in α-Fe2O3 to Fe0 may be caused by electrochemical reduction. In contrast, after the first discharge, the electrodes exhibited high charge capacities of more than 700mAhg−1 corresponding to 4.2 Li per α-Fe2O3 in the first charging (lithium extraction) process. The coulombic efficiency at the first cycle was about 70%, suggesting a valence deviation from Fe0 to Fe2+ or Fe3+ caused by electrochemical oxidation.
The decrease in the efficiency and capacity of a vanadium redox flow battery (VRB) caused by an electrolyte imbalance is an important impediment to its long-term operation. Knowing the state of charge (SOC) of an electrolyte solution can quantify the level of the electrolyte imbalance in the VRB. In this study, a four-pole cell device is devised and employed to predict the SOC. The proposed method directly measures the ionic resistance of the electrolyte solution and is sufficiently precise to be applied in real-time mode. Experimental studies on the effects of the operating current on the four-pole cell and the concentrations of vanadium and sulfuric acid in the electrolyte solution are carried out. The results show that the four-pole cell method can be utilized to measure the electrolyte SOC. The concentrations of vanadium and sulfuric acid in the electrolyte solution affect the ionic resistance of the solution. Regarding the capacity and efficiency of the VRB system, the results indicate that the electrical charge is determined from the concentration of vanadium and that the cell voltage depends on the concentration of sulfuric acid in the electrolyte solution. The decreased vanadium concentration and increased sulfuric acid concentration improves the cell voltage efficiency.
Sn/C non-woven film has been prepared by electrospinning and carbonization treatment. Investigation of scanning electron microscopy (SEM), transmission electron microscopy (TEM) and high resolution transmission electron microscopy (HRTEM) indicate that the film is formed by non-woven fibers. The fibers consist of amorphous carbon and homogeneously dispersed tin particles, which are extremely tiny (around 1nm). However, partial tin particles are oxidized when the film is kept in the air, which is confirmed by X-ray diffraction (XRD). The XRD measurement also suggests that the tin oxides completely decompose to pure tin after several electrochemical cycles. The reversible capacity of the film in the 20th cycle is 382mAhg−1, which is 96.7% of the capacity in the first cycle. Such Sn/C non-woven film could be a promising anode material in lithium ion batteries.
Summary Aims This study attempts to determine the type and relative frequency of muscle diseases contributing to floppy and hypotonic infants in Singapore. Methods Eighty consecutive muscle biopsies in the Department of Pathology, National University of Singapore, in the period 1978–2000, in which a clinical diagnosis of floppy or hypotonic infant was made, were reviewed. Results The commonest cause of severe hypotonia in infancy was spinal muscular atrophy, which accounted for 33% of cases followed by congenital muscular dystrophy (13%). Eight cases (10%) of infantile type II glycogenosis (Pompe’s disease) were encountered. There were seven cases of congenital myopathy, of which four were centronuclear myopathy, and one each of central core myopathy, nemaline myopathy and congenital fibre type disproportion. One case of centronuclear myopathy was associated with type I fibre smallness. Type II atrophy, which is generally considered a non-specific change, was encountered in five cases. Of interest is the relatively large number of muscle biopsies (29%) in which no significant pathological features were encountered at the light microscopic, histochemical as well as ultra-structural level. Conclusions The study has revealed a great variety of pathology affecting the muscle of children presenting as floppy infants or with hypotonia. The muscle diseases included spinal muscular atrophy, congenital muscular dystrophies, congenital myopathies and metabolic myopathies. However, 23 (29%) cases showed no significant pathology. For this group of floppy and hypotonic infants further studies are needed.
A variety of mechanisms lead to the failure of lithium-ion batteries. One is overcharge, a condition in which a battery's voltage rises above its designed end-of-charge potential. Electrolyte additives called redox shuttles limit cell potential by preferentially oxidizing, and cycling between the cathode and anode in their radical cation and neutral forms. Currently, testing requires coin cell assembly and repeated cycling, which can be an expensive and time consuming process. It is commonly accepted that degradation of the radical cation form of a redox shuttle leads to overcharge protection failure. We thus studied the stability of the radical cation forms of a series of redox shuttle additives to determine if there is a correlation between radical cation stability and the number of cycles of overcharge protection. While the reversibility of oxidations in cyclic voltammetry did not correlate to trends in overcharge performance, results from both UV-vis and electron paramagnetic resonance spectroscopy showed a correlation between stability and overcharge protection. Our results reveal trends within a few hours for what otherwise takes months of battery cycling to determine, providing a fast and relatively inexpensive method for predicting redox shuttle performance.
We develop three novel enhanced mixed integer-linear representations of the power limit of the battery and its efficiency as a function of the charge and discharge power and the state of charge of the battery, which can be directly implemented in large-scale power systems models and solved with commercial optimization solvers. Using these battery representations, we conduct a techno-economic analysis of the performance of a 10 MWh lithium-ion battery system testing the effect of a 5-min vs. a 60-min price signal on profits using real time prices from a selected node in the MISO electricity market. Results show that models of lithium-ion batteries where the power limits and efficiency are held constant overestimate profits by 10% compared to those obtained from an enhanced representation that more closely matches the real behavior of the battery. When the battery system is exposed to a 5-min price signal, the energy arbitrage profitability improves by 60% compared to that from hourly price exposure. These results indicate that a more accurate representation of li-ion batteries as well as the market rules that govern the frequency of electricity prices can play a major role on the estimation of the value of battery technologies for power grid applications.
Electrochemical impedance spectroscopy of batteries and fuel cells suffers from ambiguity due to overlapping features of different electrochemical processes. One approach to mitigate this problem is the analysis of impedance data by the distribution of relaxation times (DRT) of the underlying physico-chemical processes. In this work an evolution of DRT analysis using generalized Tikhonov regularization with a uniform penalty and an RC kernel is discussed. By conducting the transformation without discriminating or constraining the sign of the distribution and by using both the imaginary and the real part of the RC kernel it can be distinguished between impedance contributions of RQ-like physico-chemical processes, pure ohmic resistances and inductances in the system under investigation. Furthermore, regularization can be simultaneously applied in a second, non-inverted dimension, which affords an increased resolution of the spectrum. The properties of the algorithm are demonstrated by analyzing synthetic impedance data.
Lithium vanadium oxide (Li1+x V3O8, x =0.2) cathode materials were synthesized via a simple hydrothermal reaction followed by heat treatment at elevated temperatures, and the electrochemical performance of as-synthesized LiV3O8 as a cathode material for lithium ion batteries was investigated using galvanostatic discharge–charge cycling and electrochemical impedance spectroscopy. It reveals that different thermal treatment histories resulted in drastic changes in sizes/morphologies and electrochemical properties. The samples that were heat treated at 300°C contained many nanorod-like particles, particularly at the surface of agglomerated LiV3O8 particles. Such nanorod-shaped Li–V–O compounds exhibit two different crystal structures: either a defective LiV3O8 or a Li0.3V2O5 structure. In addition, the nanorod-shaped Li–V–O compounds in the galvanostatically cycled samples could not be observed using high-resolution scanning electron microscopy (HRSEM) because of their structural instability, which can be attributed to the deterioration of their electrochemical properties during cycling. In contrast, the samples treated at 400 and 500°C exhibited a bi-modal particle distribution and estimated sheet-like morphologies with no impurities, respectively. They also indicated excellent electrochemical properties.
This paper is focused on neutral aqueous medium, i.e.lithium, sodium and potassium sulfate solutions in a wide range of concentrations (0.1–2.5 mol L−1) as promising electrolytes for electrochemical capacitors because they are cheap, non-corrosive and allow applying diverse current collectors. These properties make the capacitor assembling process much easier and cheaper. Additionally, such electrolytes are electrochemically stable and environmentally friendly. Electrochemical investigations carried out especially for 1 mol L−1Li2SO4 aqueous solution confirmed the possibility of efficient capacitor work in a wider voltage range, i.e. even at 2.2 V without any significant capacitance fade during 15000 cycles. The physicochemical properties of ions (i.e. solvation, diffusion or mobility) and their influence on the capacitor electrochemical behaviour are considered.
Microbial biofilms can be valuable in many biotechnological applications, including bioremediation. We have previously constructed a recombinant strain of Caulobacter crescentus JS4022/p723-6H by inserting a hexahistidine peptide to a permissive site of the host surface layer (S-layer) protein RsaA. This engineered strain is highly effective in removal of cadmium from water as free cells. In this communication, we examined the biofilms formed by self-immobilized JS4022/p723-6H and evaluated their ability to retrieve cadmium from contaminated water samples. According to light and electron microscopic observations, JS4022/p723-6H cells developed a uniform monolayer biofilm on borosilicate surfaces through their intrinsic appendage, a stalk with an adhesive holdfast. The density of the biofilms reached a maximum after 48 h of incubation and was not affected by exposure to at least 1 ppm cadmium. When 0.4 ppm Cd(II) was added to the growth medium, immobilized JS4022/p723-6H removed 76.9% of the total metal, whereas the control strain only removed 13.5%. When a water sample collected from Lake Erie was spiked with various amounts of CdCl2, immobilized JS4022/p723-6H was able to sequester 44∼51% of the total metal, compared to 37∼42% accumulated by the control strain. By combining two powerful techniques, cell surface display and self-immobilization, we achieved complete separation of dissolved heavy metals from contaminated water in a single step. This study laid down the foundation to cost-effectively construct large-scale bioreactors with high efficiency and specificity to retrieve environmental contaminants from water.
A valid and facile template carbonization route for producing nanoporous carbons with hierarchical porosities has been implemented by using thiocarbanilide as carbon/nitrogen precursor, and commercially available Mg(OH)2 or Ca(OH)2 powder as template. This work is to clarify the significance and difference between Mg(OH)2 and Ca(OH)2 being as templates. The mass ratio of thiocarbanilide and Mg(OH)2 or Ca(OH)2, as well as the carbonization temperature plays crucial role in determining the pore structures and the resultant capacitive behaviors. It reveals that carbon-Mg sample whose template is Mg(OH)2 (with a mass ratio of 1:2 at 700°C) exhibits the amorphous feature with low graphitization degree. Similar result also occurs in the case of the carbon-Ca sample. The carbon-Mg sample presents high specific surface area (1018.48m2 g−1), large pore volume (5.29cm3 g−1), while those of the carbon-Ca sample are 429.11m2 g−1 and 2.52cm3 g−1, respectively. The carbon-Mg sample delivers a high specific capacitance of 327.4Fg−1 at a current density of 1.0Ag−1, as well as a large energy density of 45.47Whkg−1 at a power density of 0.5kWkg−1 in comparison with carbon-Ca sample of (260.0Fg−1) and (36.11Whkg−1). What’s more, the carbon-Mg sample exhibits higher capacitance retention of 95.45% after 10,000 charge/discharge cycles than carbon-Ca sample of 91.62% in 6molL−1 KOH electrolyte. Using Ca(OH)2 or Mg(OH)2 as template by a template carbonization route provides a simple but feasible protocol to achieve nanoporous carbons with precisely controlled architecture and hierarchical porosities.
MicroRNAs (miRNAs) are a class of highly conserved endogenous non-coding small RNAs crossing kingdoms of organisms. By searching known miRNAs identified from plant species against tomato nucleotide sequences, 13 pre-miRNAs of the nine mature miRNAs were found, amongst, six had been cloned. To confirm our prediction, a miRNA-detecting microarray was designed with probes complementary to all non-redundant mature plant miRNAs documented to date. After hybridizing with small RNAs extracted from tomato leaf tissue, 78 highly expressed mature miRNAs were detected, including all the miRNAs predicted above. Conformation of some miRNAs expression by Northern hybridization indicated that they were highly accumulated not only in leaf tissues but also in roots and stems. Additional BLAST searches with newly recognized miRNAs against tomato mRNAs from NCBI yielded 23 potential targets mainly associated with the phase change from vegetative to generative growth, with flower development and with responding to plant hormone and virus stress.
The aim of this research is to recover discarded sulfated lead-acid batteries. In this work, the effect of two methods (inverse charge and chemical charge) on the reactivation of sulfated active materials was investigated. At the inverse charge, the battery is deeply discharged and the electrolyte of battery is replaced with a new sulfuric acid solution of 1.28gcm−3. Then, the battery is inversely charged with constant current method (2A for the battery with the nominal capacity of 40Ah) for 24h. At the final stage, the inversely charged battery is directly charged for 48h. Through these processes, a discarded battery can recover its capacity to more than 80% of a similar fresh and non-sulfated battery. At the chemical charge method, there are some effective parameters that including ammonium persulfate [(NH4)2S2O8] concentration, recovery temperature and recovery time. The effect of all parameters was optimized by one at a time method. The sulfated battery is deeply discharged and then, its electrolyte was replaced by a 40% ammonium persulfate solution (as oxidant) at temperature of 50°C. By adding of oxidant solution, the chemical charging of positive and negative plates was performed for optimum time of 1h. The chemically charged batteries were charged with constant voltage method (2.66V for the battery with nominal voltage and nominal capacity of 2V and 10Ah, respectively) for 24h. By performing of these processes, a discarded battery can recovers its capacity to more than 84% of the similar fresh and non-sulfated battery. Discharge and cyclelife behaviors of the recovered batteries were investigated and compared with similar healthy battery. The morphology and structure of plates was studied by scanning electron microscopy (SEM) before and after recovery.