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The carbon material was modified by RF plasma with various reactive gases: O2, Ar and CO2. Physicochemical properties of the final carbon products were characterized using different techniques such as gas adsorption method and XPS. Plasma modified materials enriched in oxygen functionalities were investigated as electrodes for supercapacitors in acidic medium. The electrochemical measurements have been carried out using cyclic voltammetry, galvanostatic charge/discharge and impedance spectroscopy. The electrochemical measurements have confirmed that capacity characteristics are closely connected with a type of plasma exposition. Modification processes have an influence on the kind and amount of surface functional groups in the carbon matrix. The moderate increase of capacity of carbon materials modified by plasma has been observed using symmetric two-electrode systems. Whereas investigations made in three-electrode system proved that the suitable selection of plasma modification parameters allows to obtain promising negative and positive electrode materials for supercapacitor application.
The garnet-type Li+ ion conductor Li7La3Zr2O12 (LLZO) is a promising candidate as a solid electrolyte for all-solid-state Li-ion batteries. Significant progress towards understanding the structure and properties of LLZO, conventionally synthesized using solid state reaction methods, has already been made in the last decade. The aim of this review is to summarize recent efforts on the synthesis of nanostructured LLZO, with a focus on electrospinning, cellulose templating, and low-temperature (< 900°C) sol-gel based methods, as well as to highlight the unique properties of nano-sized LLZO. Further research is still needed to fully understand the potential benefits of using nanostructured LLZO in pellet-type, ceramic electrolytes, but a natural opportunity for nanostructured LLZO is in the role of ceramic filler within solid composite polymer electrolytes (CPEs). The current status of CPEs embedded with LLZO ceramic fillers is summarized, including the elucidation of Li+ transport pathways using nuclear magnetic resonance (NMR) spectroscopy.
Novel polyvinyl formal (PVFM) based gel polymer electrolytes (GPEs) are developed using an initiator free thermal polymerization method. The polymerization mechanism during the cross-linking process is investigated by means of Fourier transform infrared (FTIR) spectroscopy measurements. With the prepared GPEs (containing 2 to 5 wt % PVFM), Li polymer batteries with LiFePO4 as the cathode are assembled, and the electrochemical properties such as interfacial impedance, electrochemical stability window and cycling performance are evaluated. The resulting PVFM based GPEs present a better thermal stability compared with the corresponding conventional liquid electrolyte and an acceptable conductivity of ∼10−3 S cm−1 at ambient temperatures. Cyclic voltammetric (CV) curves reveal that the electrochemical stability window of PVFM based GPE is 1.5–5V vs. Li/Li + and wider than that for the corresponding liquid electrolyte which is 1.8–4.4 V. The discharge capacity of the polymer Li/LiFePO4 battery is 145 mAh g−1 over a voltage range of 2.5–4.25 V at 1/10 C rate after 80 cycles with a small capacity fade.
People often want to know the root cause of things and events in certain application domains such as intrusion detection, medical diagnosis, and fault diagnosis. In many of these domains, a large amount of data is available. The problem is how to perform root cause analysis by leveraging the data asset at hand. Root cause analysis consists of two main functions, diagnosis of the root cause and prognosis of the effect. In this paper, a method for root cause analysis is proposed. In the first phase, a causal knowledge model is constructed by learning a Bayesian belief network (BBN) from data. BBN’s backward and forward inference mechanisms are used for the diagnosis and prognosis of the root cause. Despite its powerful reasoning capability, the representation of causal strength in BBN as a set of probability values in a conditional probability table (CPT) is not intuitive at all. It is at its worst when the number of probability values needed grows exponentially with the number of variables involved. Conversely, a fuzzy cognitive map (FCM) can provide an intuitive interface as the causal strength is simply represented by a single numerical value. Hence, in the second phase of the method, an intuitive interface using FCM is generated from the BBN-based causal knowledge model, applying the migration framework proposed and formulated in this paper.
There is an increasing interest in the production of chemicals and fuels from renewable resources due to the continuing price increase of fossil resources, the insecurity of the availability of fossil resources in the future, and additionally environmental concerns and legislations. Biobutanol may be produced by the acetone–butanol–ethanol (ABE) fermentation. This paper reviews the biobutanol production bringing up the problems and challenges to overcome. The aim of the paper is to help in finding opportunities to make the process feasible in the near future. The analysis stresses the idea of improving the efficiency of the fermentation stage by altering the up (pretreatment of the raw material) and downstream (product recovery and purification) processes. The paper also explores the biobutanol production from the biorefinery perspective. Finally the review brings up the important role of research in developing and implementing the production of biobutanol by the ABE fermentation.
Gel polymer electrolyte membranes composed of poly(vinylidene fluoride-hexafluoropropylene) (PVdF-HFP) and surface modified aluminum or titanium oxide were prepared according to the so-called Bellcore process. Modifications were done by impregnating ceramic powder with 1–8% sulphuric acid aqueous solutions. Filler grain size varied from 10 to 12μm. The membranes were conditioned in liquid electrode—1mol/l LiClO4 in PC. The ionic conductivity of polymer membrane increased by more than one order of magnitude upon the addition of filler into polymer host. For electrolyte membrane containing modified aluminum or titanium oxide, the interfacial resistance is stable in time as opposed to unmodified gel electrolytes. An increase in lithium transference number is observed upon the addition of filler. Lithium transference number also increases with the fraction of acidic surface groups.
We report for the first time the development of irreversible compressive stresses in graphitic carbon electrodes during cycling in a Li-ion battery. The CVD grown c-axis oriented graphitic carbon thin film electrodes show that significant irreversible stresses develop in the first cycle, and then decrease with increasing number of cycles. The net irreversible compressive stress is roughly a factor of 4 higher than the actual Li-intercalation induced reversible compressive stress. A major fraction of the irreversible stress developed at potentials higher than the Li-intercalation potential, starting from ∼1.1V and increasing in intensity from ∼0.75V. Also, the variation of the irreversible stress with number of cycles follows very closely the variation of the irreversible capacity with cycle number. Measurements on carbon films with different thicknesses show that the irreversible stress is primarily a surface phenomenon. These stresses were also largely absent in films coated with a thin (0.5nm) Al2O3 layer. Analysis of all of these observations indicates that SEI layer formation is a primary cause of the irreversible stress, along with some likely contribution from solvated Li-ion co-intercalation. The magnitude of these stresses is large enough to have a significant impact on the performance and cycle life of graphitic carbon electrodes.
Hierarchical porous carbon microparticles (HPCMs) are produced by milling and sieving porous monolithic carbon, which was obtained by carbonization of a resorcinol-formaldehyde gel in the presence of surfactant as a pore stabilizer. The obtained HPCMs has a surface area of 536m2 g−1 and maximum specific capacitance and areal capacitance, measured at slow scan rates, of 194Fg−1 and 152mFcm−2 respectively. Moreover, the carbon surface remains accessible at 100mVs−1 with large values of specific capacitance (154Fg−1) and areal capacitance (121mFcm−2), making the material suitable for fast supercapacitors. The HPCMs are then built into electrostatic self-assembled (ESA) adsorbed layers by sequential immersion of a planar electrode in HPCMs dispersions and a cationic polyelectrolyte. Using soluble redox molecules, it is possible to detect the finite (inside the pores) and semi-infinite (outer surface) diffusion of redox species. The specific capacitance of the HPCMs could be increased up to 5 times (to ca. 900Fg−1 in acid media) by adsorption of naphthoquinone molecules on the carbon surface. Using the ESA process, it is possible to build a layer with three different quinones in a single electrode. The specific capacitance of those layers is more than 4 times higher and maintained nearly constant in a wide range of potential.
Conventional phosphorus anode materials in lithium/sodium-ion batteries are mainly based on the physical mixing and evaporation/condensation, in which external phosphorus on conductive matrix is unavoidable and hard to be removed due to the formation of crystalline phase. It has been found to break off from conductive matrix easily and deteriorate capacity rapidly. In this communication, we first report a solution processed encapsulation method which facilitates phosphorus anchored inside multi-walled carbon nanotubes (MWCNTs). Any possible external phosphorus adsorbents are hard to transform into crystalline and enable an easy removal by polar solvents. Eventually, the phosphorus rings and chains are successfully encapsulated only inside MWCNTs, exhibiting high cycling stability in lithium-ion battery because of the efficient physical confinement and unique discrete phosphorus segment assemblies inside MWCNTs which ensured enough vacant space for volume expansion.
In this paper we propose a novel economic robust predictive controller for periodic operation. The proposed controller joins dynamic and economic trajectory planning and robust predictive controller for tracking in a single layer taking into account bounded disturbances, algebraic constraints and periodic operation. We study the closed-loop system properties of the proposed controller and provide a design procedure that guarantees that the perturbed closed-loop system converges asymptotically to the optimal economic reachable periodic trajectory, constraint satisfaction and recursive feasibility. The proposed controller has been applied to control a cluster of interconnected micro-grids. Each nano-grid is connected to an electric utility and has a renewable energy source, a cluster of batteries and a metal hydride based hydrogen storage system. The cluster must satisfy a periodic energy demand while maximizing the profit of the energy sold to the electric utility taking into account time varying prices.
Solid polymer electrolytes are potentially useful electrolytes to be applied in high-energy batteries. In the present work, a novel polymer electrolyte, polyethylene oxide (PEO)–NaSCN–AlCl3, was prepared and investigated by FT-IR spectroscopic techniques. Based on the FT-IR data, the bands in the CN stretching envelope have been assigned and the effect of AlCl3 on ion–ion and ion–polymer interactions in the polymer electrolyte has been examined. It is shown that the Lewis acid–base interaction of AlCl3 with SCN1− leads to the formation of the complex anions AlCl3SCN− and Al2Cl6SCN−, depending on the content of AlCl3 and/or NaSCN in PEO; the preferential interactions of AlCl3 with crystal complex P(EO)3NaSCN occur in PEO–NaSCN–AlCl3 electrolytes; the AlCl3–NaSCN complex anions can play a plasticization role in PEO–NaSCN–AlCl3 electrolyte, and are expected to be a important factor to improve the conductivity and to enhance the cation transference number. In addition, the interactions between AlCl3 and ether oxygen of PEO were analyzed, and their effect on ionic association was also discussed.
The Br2/Br− oxidation–reduction couple is employed as the positive electrolyte in some redox flow batteries, such as zinc–bromine, vanadium–bromine, and hydrogen–bromine batteries. However, the Br2 and Br− crossover behavior with the proton exchange membrane is detrimental in these flow batteries. To explore the mechanism of the Br2 and Br− crossover, a spectrophotometer and a special reagent were developed to detect the accumulative penetration of the Br2 and Br− in the negative electrolyte. In addition, a laboratory-designed quinone–bromine flow battery was developed to investigate the effect of Br− and Br2 crossover behavior on cell performance. What’s more, molecular dynamics simulations of Br− and Br2 passing through a membrane were performed to analyze Br− and Br2 crossover behavior. It can be concluded that Br2 crossover was the key factor contributing to the current inefficiency. The coulombic efficiencies increased from 72.5 to 82.5 to 90% as the current density increased from 0.025 to 0.075 A cm−2 which occurred due to Br species crossover. The cell performance factors are strongly related to the amount of Br2 crossover; hence, these factors will vary as the bulk aqueous phase Br species concentration changes.
Nano-Ni3Sn2 intermetallic compound was successfully prepared by solvothermal method for an anode material of lithium-ion batteries. Its microstructure was characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). Electrochemical performances were evaluated in a lithium-ion model cell Li/LiPF6 (EC+DMC)/Ni3Sn2. The electrochemical lithiation and de-lithiation behavior of nano-Ni3Sn2 was investigated by ex situ XRD. Diffraction peaks of Ni3Sn2 widened and shrank gradually during lithiation. Sharp Ni3Sn2 peaks appeared again after full de-lithiation. It was proved that nano-Ni3Sn2 could be reversibly charged and discharged with lithium though the de-lithiation capacity of nano-Ni3Sn2 was lower than its theoretical capacity.
In this work, N-doped biomass derived porous carbon (NSBDC) has been prepared utilizing low-cost agricultural waste--sugarcane bagasse as the prototype, and needle-like PANI as the dopant. NSBDC possesses a special 3D interconnected framework structure, superior hierarchical pores and suitable heteroatom doping level, which benefits a large number of applications on ion storage and high-rate ion transfer. Typically, the NSBDC exhibits the high specific capacitance (298 F g−1 at 1 A g−1) and rate capability (58.7% capacitance retention at 20 A g−1), as well as the high cycle stability (5.5% loss over 5000 cycles) in three-electrode systems. A two-electrode asymmetric system has been fabricated employing NSBDC and the precursor of NSBDC (sugarcane bagasse derived carbon/PANI composite) as the negative and positive electrodes, respectively, and an energy density as high as 49.4 Wh kg−1 is verified in this asymmetric system. A NSBDC-based whole symmetric supercapacitors has also been assembled, and it can easily light a 1.5 V bulb due to its high energy density (27.7 Wh kg−1). In addition, for expanding the application areas of NSBDC, it is also applied to lithium ion battery, and a high reversible capacity of 1148 mAh g−1 at 0.1 A g−1 is confirmed. Even at 5 A g−1, NSBDC can still deliver a high reversible capacity of 357 mAh g−1 after 200 cycles, indicating its superior lithium storage capability.
The electrochemical behavior and the stability under cycling of TiSnSb anode for Li-ion batteries were investigated in room temperature ionic liquids based electrolyte. X-ray photoelectron spectroscopy (XPS), cyclic voltammetry, and electrochemical impedance (EIS) measurements have been performed to study the formation of surface film on the TiSnSb anode. Surface analysis was performed by a combined XPS core peaks and quantification data analysis, to establish the main components of the solid electrolyte interphase film (SEI). The key observation is that the thickness and the chemical nature of the SEI layer is strongly related to the electrolyte formulation and the addition of SEI layer forming additives. Vinylene carbonate (VC) and fluoroethylene carbonate (FEC) were applied in order to improve the anode/electrolyte interface. From XPS, EIS results and galvanostatic cycling the role of additives and ionic liquids as an effective stability improver has been highlighted.
Emphasis on early identification of atypical development has increased as evidence supporting the efficacy of intervention has grown. These increases have also directly affected the availability of funding and providers of early intervention services. A majority of research has focused on interventions specific to an individual's primary diagnoses. For example, interventions for those with cerebral palsy (CP) have traditionally focused on physiological symptoms, while intervention for individuals with Autism Spectrum Disorder (ASD) focus on socialization, communication, and restricted interests and repetitive behaviors. However deficits in areas other than those related to their primary diagnoses (e.g., communication, adaptive behaviors, and social skills) are prevalent in atypically developing populations and are significant predictors of quality of life. Therefore, the purpose of the current study was to examine impairments in socialization and nonverbal communication in individuals with Down's syndrome (DS), CP, and those with CP and comorbid ASD. Individuals with comorbid CP and ASD exhibited significantly greater impairments than any diagnostic group alone. However, individuals with CP also exhibited significantly greater impairments than those with DS. The implications of these results are discussed.
LiFe1−x Nd x PO4/C (x =0–0.08) cathode material was synthesized using a solid-state reaction. The synthesis conditions were optimized by thermal analysis of the precursor and magnetic properties of LiFePO4/C. The structure and electrochemical performances of the material were studied using XRD, FE-SEM, EDS, electrochemical impedance spectroscopy and galvanostatic charge–discharge. The results show that a small amount of aliovalent Nd3+ ion-dopant substitution on Fe2+ ions can effectively reduce the particle size of LiFePO4/C. Cell parameters of LiFe1−x Nd x PO4 (x =0.04–0.08) were calculated, and the results showed that LiFe1−x Nd x PO4/C had the same olivine structure as LiFePO4. LiFe0.4Nd0.6PO4/C delivers the discharge capacity of 165.2mAhg−1 at rate of 0.2C and the capacity retention rate is 92.8% after 100 cycles. Charge-transfer resistance decreases with the addition of glucose and Nd3+ ions. Poly(cyclotriphosphazene-co-4,4′-sulfonyldiphenol) (PZS) was synthesized and PZS nanorods were used as a carbon source to coat LiFePO4. All of the results show that aliovalent doping substitution of Fe in LiFePO4 is well tolerated.
LiNi0.5−x Co2x Mn1.5−x O4 (0≤2x ≤0.2) was prepared by spray drying, then re-annealing in O2. Their structural and electrochemical properties were studied by ex-situ XRD, GITT, and charge–discharge testing. The substitution of cobalt for Ni and Mn in the LiNi0.5Mn1.5O4 resulted in significant structural and electrochemical variations, such as the change in structural transformation with lithium extraction, the increase in the lithium diffusion coefficient and the decrease in the area specific impedance. Moreover, the improved kinetic properties caused by the Co substitution for Ni and Mn result in an improved cyclic performance at a high rate and at elevated temperature as well as the rate capability.
Studies of sentence comprehension deficits in Parkinson’s disease (PD) patients suggest that language processing involves circuits connecting subcortical and cortical regions. Anatomically segregated neural circuits appear to support different cognitive and motor functions. To investigate which functions are implicated in PD comprehension deficits, we tested comprehension, verbal working memory span, and cognitive set-switching in a non-linguistic task in 41 PD patients; we also obtained speech measurements reflecting motor sequencing processes that may be involved in articulatory rehearsal within working memory. Comprehension of sentences with center-embedded or final relative clauses was impaired when they could not be understood from lexical semantic content alone. Overall comprehension error rates correlated strongly with impaired set-switching and significantly with reduced working memory span and speech motor sequencing deficits. Correlations with comprehension of different sentence structures indicate that these impairments do not represent a single deficit; rather, PD comprehension deficits appear to arise from several independent mechanisms. Deficits in cognitive set-switching or underlying inhibitory processes may compromise the ability to process relative clauses. Deficits in verbal working memory appear to impair comprehension of long-distance dependencies. Speech sequencing correlated with neither set-switching nor verbal working memory span, consistent with their being supported by independent, segregated cortico-subcortical circuits.
Redox active organic molecules (ROMs) are promising candidates for redox flow battery (RFB) energy storage due to their high sustainability and low cost. Herein, the pseudooxocarbon derivative croconate violet (Croc2-) is applied as a novel symmetric ROM in acetonitrile electrolyte, whereby Croc2- is used as both the battery posolyte and negolyte, with a 1.82 V cell potential and ≃1 M solubility. Characterisation of the dianion Croc2- is given by way of voltammetry and battery cycling techniques to demonstrate the high number of oxidation states accessible by Croc2-, thus highlighting a high intrinsic capacity for a low molecular weight ROM. The stability of Croc2- and its charged radical states is investigated to assess the viability of the symmetric design, and an undesirable radical disproportionation mechanism of the Croc•3- oxidation state is identified to account for poor capacity retention. Asymmetric battery experiments of a Croc2- posolyte with 2,1,3-benzothiadiazole or tetracyanoquinodimethane negolytes gave improved battery performance, indicating that Croc2- is a promising anionic ROM posolyte.
Direct oxidation fuel cell (DOFC) based on proton conducting membranes (PCM's) represents a promising energy technology, with the vast majority of efforts devoted to methanol as the fuel. The most commonly used PCM is Nafion. However, because of high production cost, high fuel crossover, and sensitivity to metal-ion impurities, alternative materials are being developed. Methanol presents several limitations including low boiling point (∼65°C), and reduced cell efficiency due to fuel crossover. We present here a measure of the mass transport represented by the self-diffusion coefficients (D) of methanol, and two alternative fuels—ethylene glycol (EG) and dimethyl oxalate (DMO) in new low-cost nanoporous (NP) PCM's. The NP-PCM's are based on commercial poly(vinylidene fluoride), with variable pore size determined by the addition of nanoscale SiO2 or TiO2 particles. Proton NMR pulsed gradient spin-echo (PGSE) self-diffusion measurements were conducted on aqueous solutions of 2 M fuel in 3 M H2SO4 and also on five NP-PCM equilibrated in the aqueous solutions over the temperature range of 30–90°C. Here the fuel molecular mobility is indicated by the D values of the methyl and methylene peaks. Results indicate that both DMO and EG solutions have lower fuel molecular mobility than methanol. Results for the various NP-PCM also reveal reduced fuel permeability for DMO and EG compared with methanol.