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A theoretical impedance function for the anodic dissolution of nickel is developed by considering the hypothesis that there are two competitive anions which participate in the stabilization of the electrogenerated Ni(II) species. The experimental effect of chloride ion concentration on nickel electrodissolution process is analyzed by means of a mechanism that considers this competency. It is observed that an increased Cl− concentration causes an increase in Ni(I) surface concentration and a decrease in the kinetic constant rates of the considered mechanism. Moreover, an increased chloride concentration causes a flattening in the low frequencies inductive loop in the Nyquist plot recorded at relatively low stabilization potentials. In the active anodic dissolution/passive transition potential range chloride ions favours a salt layer precipitation which interferes with the passive layer formation.
In this contribution we present a soft matter solid electrolyte which was obtained by inclusion of a polymer (polyacrylonitrile, PAN) in LiClO4/LiTFSI–succinonitrile (SN), a semi-solid organic plastic electrolyte. Addition of the polymer resulted in considerable enhancement in ionic conductivity as well as mechanical strength of LiX–SN (X=ClO4, TFSI) plastic electrolyte. Ionic conductivity of 92.5%-[1M LiClO4–SN]:7.5%-PAN (PAN amount as per SN weight) composite at 25°C recorded a remarkably high value of 7×10−3 Ω−1 cm−1, higher by few tens of order in magnitude compared to 1M LiClO4–SN. Composite conductivity at sub-ambient temperature is also quite high. At −20°C, the ionic conductivity of (100− x)%-[1M LiClO4–SN]:x%-PAN composites are in the range 3×10−5–4.5×10−4 Ω−1 cm−1, approximately one to two orders of magnitude higher with respect to 1M LiClO4–SN electrolyte conductivity. Addition of PAN resulted in an increase of the Young's modulus (Y) from Y →0 for LiClO4–SN to a maximum of 0.4MPa for the composites. Microstructural studies based on X-ray diffraction, differential scanning calorimetry and Fourier transform infrared spectroscopy suggest that enhancement in composite ionic conductivity is a combined effect of decrease in crystallinity and enhanced trans conformer concentration.
KEYWORDS Hearing protector, stability, active control of sound, safety, wearable, human friendly
In this review paper we summarize recent research trends for polymer fuel cells (PEMFCs) that utilize various graphene materials described in articles published since 2007. We propose to analyze the influence of graphene in PEMFCs in three aspects: (i) as an electrode (anode or cathode), (ii) as an additive to polymer electrolyte and (iii) as a filler to bipolar plates along with some discussions on future research directions. In Section 2 of this review, we shortly present the fundamental processes of fuel cells along with important parameters such as hydrogen oxidation and oxygen reduction reactions, polarization losses, exchange current density, open circuit voltage and efficiency for fuel cells. Additionally, with curt description of various kinds of fuel cells and types of polymers applied in PEMFCs. Moreover, we discuss briefly different synthetic routes of graphene and describe selected graphene properties (Section 3). In Section 4, we analyze in detail the possibilities of applied graphene or its derivatives in various places in PEMFCs. Graphene applied to PEMFCs has a significant contribution on the increased electrical or ionic conductivity, better mechanical durability and corrosion resistance, and higher electrochemical surface area, depending on the fuel cell component that is modified. For instance, taking into consideration the function of graphene in polymer fuel cells and based on the current review, the highest value of maximum power density of 0.742Wcm−2 was found for PEMFC with graphene utilized as an anode support. The promising results open the way for the usage of graphene as a prospective material for application in fuel cells. However, the main difficulty of graphene application is the fact that this material has to be sufficiently separated by additional compounds to prevent restacking of graphene sheets.
Fine powders of Li1.2Ni0.2Mn0.6−xMoxO2 (x=0, 0.002, 0.005, 0.01, 0.05) are prepared by a thermopolymerization method. X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy and electrochemical measurements are carried out to characterize these samples. The maximum Mo-doping level to obtain a pure layered phase is 0.005. The Mo-doped samples show a great improvement in rate performance and cycling stability. For the optimal composition Li1.2Ni0.2Mn0.59Mo0.01O2, it exhibits a discharge capacity of 245 and 110mAhg−1 at 0.1C and 5C, respectively. It retains a capacity of 229mAhg−1 at 0.1C after 204 cycles with a capacity retention of 93.2%. This study suggests that the partial substitution of Mn4+ with Mo6+ can improve both the rate capability and cycle performance of this high-capacity cathode material.
In situ and ex situ scanning electron microscopy of nano Si and SiO anode particles was carried out during the first cycles, and at various stages of charge. The particle size effects were explored in the range 0.1–20 μm, providing a new insight into the micro-structural evolution of the particles as a function of their size, and into the ‘mechanical’ resistance upon important volume change upon phase transformation of these anodes. For small particles, the failure of the battery comes from an electrochemical sintering that compacts the whole electrode, which results in its cracking. The particles keep their integrity when the discharge is stopped at a voltage 0.1 V, which corresponds to the chemical composition Li12Si7, while the particles are known to crack at deeper discharge up to Li22Si5. Replacing the Si particles by SiO particles in an attempt to avoid these structural effects did not help, because of the different chemical reactions during cycling, with the loss of oxygen.
Thermal management system is crucial for a Lithium-ion battery pack as cycle life, driving range of electric vehicle, usable capacity and safety are heavily dependent on the operating temperature. Optimum operating temperature of Lithium-ion battery pack is about 25–40 °C. Power availability of the battery pack may differ according to the operating temperature. Although air cooling is the simplest and cheapest cooling solution, the cooling capacity is still limited by the low specific heat capacity. This will cause large variation of temperature of cells across the battery pack. In this study, mist cooling is proposed for battery pack thermal management system. Experiments and numerical simulations are conducted to investigate the thermal performance of conventional dry air cooling and mist cooling. Simulation results are then validated with the experimental data. The simulation results show that mist cooling can offer lower and more uniform temperature distribution compared to dry air cooling. Mist cooling with mass flow rate of 5 gs−1 and 3% mist loading fraction is sufficient to ensure the surface temperature of the battery module maintained to below 40 °C. Therefore, mist cooling is a potential solution for the thermal management system of Lithium-ion battery pack.
Silicon (Si) has been considered as one of the most promising anodes in secondary high-energy rechargeable lithium-ion batteries (LIBs) owing to its high theoretical specific capacity and abundant reserves, whereas it suffers from an unstable solid electrolyte interphase (SEI) film and dramatic volume expansion. Herein, in situ electrochemical atomic force microscopy (AFM) and visual videos were used to reveal the interphasial properties of SEI film and anisotropic dynamics upon lithiation/delithiation processes on the single-crystalline Si electrodes with different crystal plane orientations. Lithiation of Si (111) prefer to grow along the <121> direction in the XY plane with the shape of oriented rods, in contrast, that of Si (100) form cone-like structure with the axial direction of <100> perpendicular to the (100) surface. Quantitative dynamic processes elucidate the preferable reversibility in Si (111) system, revealing the corresponding structure-reactivity correlations.
Electrocatalytic reduction of O2 with dual catalysts of cobalt 1, 2, 3, 4, 8, 9, 10, 11, 15, 16, 17, 18, 22, 23, 24, 25-hexadecafluoro-29 H, 31H-phthalocyanine (CoPcF16) and MnOOH was studied in alkaline media with cyclic and rotating ring-disk electrode (RRDE) voltammetry. Cyclic voltammetric results show that CoPcF16 possesses a good catalytic activity for redox-catalyzing an apparent two-electron reduction of O2 with superoxide (O2 −) as an intermediate. The combined use of CoPcF16 with MnOOH which shows a bifunctional catalytic activity toward the sequential disproportionations of the reduction intermediate and product, i.e. O2 − and peroxide (HO2 −), eventually enables an apparent four-electron reduction of O2 to be achieved at a positively-shifted potential in alkaline media. The possibility of utilizing the dual catalysts for the development of practical alkaline air electrodes was further explored by confining the catalysts in active carbon (AC) and carbon black (CB) matrices that are generally used as the substrate for constructing air electrodes. The RRDE voltammetric results suggest that an apparent four-electron reduction of O2 reduction can be obtained at the as-prepared carbon-based air electrode at a potential close to that at the Pt-based air electrode, and that the as-prepared electrode shows a high tolerance against methanol and glucose crossover.
This paper considers the effect of direct democracy on quality of life in the American States. Specifically, it seeks to determine to what extent the use of the initiative affects satisfaction with life. The theoretical discussion draws upon traditional arguments over direct democracy, along with contemporary research on the quality of representation in the United States. The empirical results suggest that satisfaction varies positively with the extent to which initiatives are used. We also find that this relationship is mediated by income, such that the positive effects of direct democracy are most pronounced for those with the lowest income. The consequences for our understanding of direct democracy, public policy, and the study of life satisfaction are discussed.
Understanding how large carnivore guilds survive in human-dominated landscapes is key to inform strategies for their conservation in the face of global carnivore declines. Amur tigers and leopards are recovering across the China-Russia border. However, knowledge is limited about competitive interactions between two large cats in Northeast Asia.
Li3-xNaxV2-xTix(PO4)3/C (x = 0, 0.01, 0.03, 0.05, and 0.07) have been prepared via a conventional sol–gel method. X-ray diffraction patterns indicate that Li3-xNaxV2-xTix(PO4)3/C are successfully obtained with a monoclinic structure. X-ray photoelectron spectroscopy has been performed to investigate the valence states of the doped elements. The morphologies of Li3-xNaxV2-xTix(PO4)3/C are investigated by field emission scanning electron microscopy. Li2.97Na0.03V1.97Ti0.03(PO4)3/C exhibits the highest electrochemical properties among all the samples. It delivers an initial discharge capacity of 170.61 mAh g−1 and capacity retention of 72.66% after 100 cycles, while the uncoated Li3V2(PO4)3/C only delivers an initial discharge capacity of 164.08 mAh g−1 and capacity retention of 71.59% in the voltage range of 3.0–4.8 V. In addition, the results of cyclic voltammetry and galvanostatic intermittent titration technique ensure that the ionic conductivity of Li2.97Na0.03V1.97Ti0.03(PO4)3/C is increased compared with the uncoated Li3V2(PO4)3/C.
We constructed a Li3V2(PO4)3/Li1.5Al0.5Ge1.5(PO4)3/Li3V2(PO4)3 symmetric all solid-state Li-ion battery. Since the rechargeable capacity of Li3+x V2(PO4)3 anode is lower than that of Li3−x V2(PO4)3 cathode, the symmetric cell capacity is restricted by the anode capacity. So, the improvement of Li3+x V2(PO4)3 anode properties was tried using mechanical milling to uniformly mix Li3V2(PO4)3 and carbon. The charge and discharge capacity of Li3V2(PO4)3/C using mechanical milling was greatly increased compared to Li3V2(PO4)3/C using hand milling. The structure change with the insertion and extraction of lithium confirmed using ex-situ XRD measurements. The Li extraction/insertion of Li3V2(PO4)3 with a NASICON structure can proceed to the reversible expansion/contraction of the lattice due to the structural strength and flexibility of NASICON framework with the corner-sharing matrix. The discharge capacity of the all solid-state battery per Li3V2(PO4)3 in cathode weight achieved 92 mAh g−1 by good dispersion state of Li3V2(PO4)3 and carbon using mechanical milling.
Layered Li[Li0.2Mn0.54Ni0.13Co0.13]O2–Spinel LiMn1.5Ti0.5O4 composite cathodes have been prepared by mechanically mixing process and investigated in this work. The unoccupied 16c sites of spinel LiMn1.5Ti0.5O4 can be used as a reservoir to store the Li+ ions that are lost during the activation of Li2MnO3 component in lithium-rich Li[Li0.2Mn0.54Ni0.13Co0.13]O2 material. As a consequence, the initial irreversible capacity loss (ICL) of lithium-rich Li[Li0.2Mn0.54Ni0.13Co0.13]O2 is significantly reduced in the presence of spinel LiMn1.5Ti0.5O4. When mixed with 35.7 wt% of LiMn1.5Ti0.5O4, the lithium-rich material shows an initial ICL of only 17 mAh g−1, and could still deliver an initial discharge capacity as high as 220 mAh g−1. More importantly, the composite materials show better cycling performance and rate capability as compared with the pristine Li[Li0.2Mn0.54Ni0.13Co0.13]O2. The material with 35.7 wt% LiMn1.5Ti0.5O4 shows the best cycling stability, retaining 90% of the initial discharge capacity at the current density of 20mAg−1 after 40 cycles. The improved cycling stability and rate performance can be ascribed to the good conductivity of spinel LiMn1.5Ti0.5O4 with 3D fast Li+ diffusion path, which ensures the timely lithium ion intercalation and de-intercalation.
The promise of high energy density lithium–sulfur batteries with long cycle life is currently tempered by the rapid degradation of lithium-metal anodes with cycling. An in-depth understanding of the dynamical behavior in liquid electrolytes, including the mechanisms underlying depletion of lithium inventory and evolution of lithium interphases, is crucial to make Li–S batteries a reality. We use here an anode-free full cell configuration, pairing a Li2S cathode with a bare nickel current collector with no lithium metal on it, to quantitatively estimate the lithium inventory loss per cycle. Lithium inventory loss is shown to be the main factor limiting the overall cyclability of Li–S batteries. Time-of-flight secondary ion mass spectrometry measurements on the deposited lithium reveal the presence of substantial metallic lithium even after most of the active lithium inventory has been depleted. The trapped metallic lithium is rendered electrochemically inactive by the growth of a resistive electrolyte decomposition interphase on the lithium surface. The bulk of the deposited lithium is shown to be composed of various fully reduced interphasial components, including several hydrogen-containing species that show a substantial reduction in intensity with cycling. This indicates considerable gas evolution and is also correlated with the loss of lithium inventory. The use of an anode-free full cell configuration provides a framework for accurate assessment of the dynamics of lithium inventory depletion and characterization of the accompanying interphasial evolution with cycling. The insights gained will prove invaluable to the development of strategies for extending the cycle life of energy-dense Li–S batteries.
The structural, electronic and ion transport properties of an amorphous member of the LiPON family with non-trivial composition and cross-linking are studied by means of electronic structure calculations within Density Functional Theory. By a combination of an evolutionary algorithm followed by simulated annealing and alternatively by a rapid quenching protocol, structural models of disordered Li5P4O8N3 are generated, which are characterized by a local demixing in Li-rich and Li-poor layers. These structures have a composition close to what is found experimentally in thin films and contain all the expected diversely coordinated atoms, namely triply- and doubly-coordinated nitrogens and bridging and non-bridging oxygens. The issue of ionic conductivity is addressed by calculating defect formation energies and migration barriers of neutral and charged point defects. Li+ interstitials are energetically much preferred over vacancies, both when the lithium reservoir is metallic lithium and LiCoO2. The competitive formation of neutral Li interstitials when LiPON is contacted with metallic Li results in the chemical reduction of LiPON and the disruption of the network, as recently observed in experiments.
Well-crystallized Mn3O4-anchored reduced graphene oxide (rGO) nanocomposites have been successfully synthesized via a facile, effective, energy-saving, and scalable microwave hydrothermal technique for potential application as supercapacitor material. Integrating these nanostructures resulted in a strong synergistic effect between the two materials, consequently leading to a hybrid composite with higher specific capacitance compared to the bare Mn3O4 nanoparticles. The results from different sorts of characterization indicate that the Mn3O4 particles were deposited and anchored on graphene sheets. The capacitance value of the rGO(31.6%)–Mn3O4 nanocomposite reached 153F/g, much higher than that of the bare Mn3O4 (87F/g) at a scan rate of 5mV/s in the potential range from −0.1V to 0.8V. More importantly, a 200% increase in capacitance was observed for the nanocomposite with cycling at 10mV/s due to electrochemical activation and the oxidization of Mn(II,III) to Mn(IV) during cycling, as verified by X-ray photoelectron spectroscopy. There is no observable capacitance fading up to 1000 cycles. The facile synthesis method and good electrochemical properties indicate that the nanocomposite could be an electrode candidate for supercapacitors.
Carboxylic acid group was introduced by radiation-induced grafting of acrylic acid (AAc) onto polyolefine nonwoven fabric (PNF), wherein the PNF comprises at least about 60% of a polyethylene having a melting temperature at ∼132°C and no more than about 40% of a second polypropylene having a lower melting temperature at ∼162°C, for a battery separator. The AAc-grafted PNF was characterized by XPS, SEM, DSC, TGA and porosimeter. The wetting speed, electrolyte retention, electrical resistance, and tensile strength were evaluated after grafting of AAc. It was found that the wetting speed, electrolyte retention, thickness, and ion-exchange capacity increased, whereas the electrical resistance decreased with increasing grafting yield. The tensile strength decreased with increasing grafting yield, whereas the elongation decreased with increasing grafting yield.
An SAR model of the induction of mutations at the tk± locus of L5178Y mouse lymphoma cells (MLA, for mouse lymphoma assay) was derived based upon a re-evaluation of experimental results reported by a Gene-Tox (GT) working group [A.D. Mitchell, A.E. Auletta, D. Clive, P.E. Kirby, M.M. Moore, B.C. Myhr, The L5178Y/tk± mouse lymphoma specific gene and chromosomal mutation assay. A phase III report of the U.S. Environmental Protection Agency Gene-Tox Program, Mutation Res. 394 (1997) 177–303.]. The predictive performance of the GT MLA SAR model was similar to that of a Salmonella mutagenicity model containing the same number of chemicals. However, the structural determinants (biophores) derived from the GT MLA SAR model include both electrophilic as well as non-electrophilic moieties, suggesting that the induction of mutations in the MLA may occur by both direct interaction with DNA and by non-DNA-related mechanisms. This was confirmed by the observation that the set of biophores associated with MLA overlapped significantly with those associated with phenomena related to loss of heterozygosity, chromosomal rearrangements and aneuploidy. The MLA SAR model derived from the GT data evaluation was significantly more predictive than an SAR model previously derived from MLA data reported by the US National Toxicology Program [B. Henry, S.G. Grant, G. Klopman, H.S. Rosenkranz, Induction of forward mutations at the thymidine kinase locus of mouse lymphoma cells: evidence for electrophilic and non-electrophilic mechanisms, Mutation Res. 397 (1998) 331–335.]. Moreover, the latter model appeared to be more complex than the former, suggesting that the GT induction data was both simpler mechanistically and more homogeneous than that of the NTP.
The effect of simultaneous cobalt as well as aluminum doping was studied to understand their effect on the phase formation behavior and electrochemical properties of solution derived lithium nickel oxide cathode materials for rechargeable batteries. The discharge capacities of LiNi0.80Co0.20O2 and LiNi0.80Co0.15Al0.05O2 cathodes, measured at constant current densities of 0.45mAcm−2 in the cut-off voltage range of 4.3–3.2V, were 100 and 136mAhg−1, respectively. LiNi0.80Co0.15Al0.05O2 had better cycleability than the LiNi0.80Co0.20O2 cathodes. The retention of undesirable Li2CO3 phase both in LiNi0.80Co0.20O2 and LiNi0.80Co0.15Al0.05O2 cathodes was argued to be responsible for the relatively lower discharge capacity of these materials.
Objective To compare nonreferred, emergency department (ED)-admitted mild traumatic brain injury (MTBI) patients with and without self-reported cognitive complaints on (1) demographic variables and injury characteristics; (2) neuropsychological test performance; (3) 12-day self-monitoring of perceived cognitive problems; and (4) emotional distress, physical functioning, and personality. Methods (Neuro)psychological assessment was carried out 6 months post-injury in 79 patients out of a cohort of 618 consecutive MTBI patients aged 18–60, who attended the ED of our level I trauma centre. Cognitive complaints were assessed with the Rivermead Postconcussional Symptoms Questionnaire (RPSQ). In addition, patients monitored concentration problems and forgetfulness during 12 consecutive days. Results Self-reported cognitive complaints were reported by 39% of the patients. These complaints were strongly related to lower educational levels, emotional distress, personality, and poorer physical functioning (especially fatigue) but not to injury characteristics. Severity of self-reported cognitive complaints was neither associated with the patients' daily observations of cognitive problems nor with outcome on a range of neuropsychological tests. Conclusion Self-reported cognitive complaints were more strongly related to premorbid traits and physical and emotional state factors than to actual cognitive impairments. In line with previous work, this suggests that treatment of emotional distress and fatigue may also reduce cognitive complaints. Cognitive outcome assessment of symptomatic MTBI patients should not be restricted to checklist ratings only, but also include a (neuro)psychological screening. In addition, daily monitoring of complaints is a useful method to gather information about the frequency and pattern of cognitive problems in daily life.