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Titanium dioxide (TiO2) materials are applied as electrode materials of Lithium-ion batteries in terms of good cycling stability. However, the poor lithium-ions batteries transport kinetics and low electronic conductivity limited the development of TiO2 as anode materials. As known, TiO2(B) is a metastable phase of titanium oxide and has better electrochemical performance than others. The crystal structure of TiO2(B) is comprised of edge and corner-sharing TiO6 octahedra which can lead to facile lithium-ion intercalation. In order to solve this problem, it is desirable to control the morphology of TiO2(B) to shorten the Li+ diffusion path. In this study, synthesized TiO2(B)/Anatase composite materials is deal anode materials for Lithium-ion batteries. The anatase makes the composite materials have long term stability. Because the anatase phase TiO2 has stable structure and it is hard to transform to other phases. Moreover, TiO2(B) provides the Li+ ion diffusion path to improve the electrochemical performance. Nowadays hydrothermal methods for the synthesis of TiO2(B) are the only reported. Herein, we report a new method to synthesize TiO2(B). The nanoparticles TiO2(B)/Anatase composite oxide can be successfully fabricated via a simple solid-state chemical reaction. The titanium oxysulfate sulfuric acid hydrate and oxalic acid are used as starting materials. The synthesis is processed with low-temperature solid-state reaction and then calcination. Compared to the traditional hydrothermal method, the synthesis process of solid-state chemical reaction is greener, simpler and eco-friendlier. This method has significant advantage in the field of nano materials synthesis. In this work, the uniformly TiO2(B)/Anatase microspheres are synthesized with a high crystalline. The synthesized TiO2(B)/Anatase displays good cycling stability and high capacity retention as an anode material for Lithium-ion batteries. This work provides a new idea for the future research of titanium oxide-based materials for anode materials.
Mixed transition-metal oxides (MTMOs) are regarded as advanced electrode materials for sodium-ion batteries (SIBs). In this study, amorphous CoSnO3 nanocubes wrapped by reduced graphene oxide (marked as a-CoSnO3@rGO) are successfully designed via a facile solvothermal method accompanied by a simple calcination process. To examine this design, sodium storage behaviors of a-CoSnO3@rGO nanocomposites are investigated in detail. Compared with the pristine a-CoSnO3, a-CoSnO3@rGO nanocomposite with 25.1 wt% rGO exhibits enhanced electrochemical performance, for instance, it delivers a high specific capacity of 229.9 mAh g−1 after 100 cycles at 50 mA g−1 with a Coulombic efficiency close to 99%, and it is capable of maintaining a specific capacity of 205.7 mAh g−1 even at a high current density of 800 mA g−1. Superior electrochemical performance of a-CoSnO3@rGO is primarily attributed to intrinsic “self-matrices”, rGO-wrapping network, and crystalline texture engineering. Indeed, the unique 3D-rGO-wrapping architecture of a-CoSnO3@rGO manifests compelling advantages, such as developing a high conductive three-dimensional network, facilitating the ion/electron diffusion, accommodating volume change, and strengthening interaction between rGO and a-CoSnO3. It is believed that the proposed strategy may provide new insights to design hybrid anode nano-materials for advanced SIBs.
Nanocomposites based on polyoxometalates (POMs) nanoconfined in microporous carbons have been synthesized and used as electrodes for supercapacitors. The addition of the pseudocapacitance from highly reversible redox reaction of POMs to the electric double-layer capacitance of carbon lead to an increase in specific capacitance of ∼90% at 1 mV s−1. However, high solubility of POM in traditional aqueous electrolytes leads to rapid capacity fading. Here we demonstrate that the use of aqueous solutions of protic ionic liquids (P-IL) as electrolyte instead of aqueous sulfuric acid solutions offers an opportunity to significantly improve POM cycling stability. Virtually no degradation in capacitance was observed in POM-based positive electrode after 10,000 cycles in an asymmetric capacitor with P-IL aqueous electrolyte. As such, POM-based carbon composites may now present a viable solution for enhancing energy density of electrical double layer capacitors (EDLC) based on pure carbon electrodes.
High-performance electrode materials consisting of intertwined caterpillar-like NiFe layered double hydroxide bridges coated on reduced graphene oxide modified Ni foam (NiFe LDHs/rGO/NF) were prepared via a facile two-step electrodeposition method. First, rGO was electrochemically coated onto NF at a constant potential of −1.2 V vs. SCE for 600 s. Then NiFe LDHs of different Ni to Fe ratios were electrodeposited onto the formed rGO/NF electrodes at −1.2 V vs. SCE for 10 s. Under optimized conditions, NiFe LDHs/rGO/NF composites displayed a high specific capacitance of 1462.5 F g−1 at a current density of 5 A g−1 and retained about 64.7% of the original capacitance after 2000 cycles. Furthermore, a flexible asymmetric supercapacitor was prepared using NiFe LDHs/rGO/NF as the cathode and mesoporous carbon (MC) coated on NF as the anode. The supercapacitor exhibited an energy density of 17.71 Wh kg−1 at a power density of 348.49 W kg−1. All of these findings suggest that the new electrodes developed in this work hold a potential application prospect in flexible energy storage devices.
This paper proposes a system-wide optimal coordinated energy dispatch method for a multi-energy microgrid in both the grid-connected and islanded modes. The studied microgrid consists of multiple energy carriers covering the controllable generation units (fuel cell, electric boiler, combined cooling, heat and power plant and electric chiller), uncontrollable generation units (wind turbine and photovoltaic cell) and energy storage devices (battery storage, heat storage tank and ice storage tank). The proposed energy dispatch method aims to minimize the microgrid net operating cost and enhance the dispatch flexibility in supplying power, heat and cooling in the day-ahead energy market. For both the grid-connected and islanded microgrid, their dispatch models are formulated as the mixed-integer linear programming problems, which can be efficiently solved by the commercial solvers. Comprehensive case studies are performed to evaluate the effectiveness of the proposed method and then compared with the traditional dispatch methods which supply power and heat/cooling energies separately. Simulation results demonstrate that the proposed method can achieve much higher operating efficiency.
Executive function deficits are among the most frequent sequela of very preterm birth but the underlying neuronal mechanisms are not fully understood. We used high-density electroencephalography (EEG) recordings during sleep to assess alterations in the functional neuroanatomy of executive processes in adolescents born very preterm. The topographical distribution of sleep slow wave activity (SWA; 1–4.5 Hz EEG power) has previously been used to map cognitive abilities and is known to reflect the intensity of the prior use of the respective neuronal networks. We assessed 38 adolescents born before 32 weeks of gestation [age at assessment: 12.9 (SD: 1.7), range: 10.6–16.7 years] and 43 term-born peers [13.1 (2.0), 10.0–16.9]. Executive function abilities were quantified with a composite score derived from a comprehensive task battery. All-night high-density EEG (128 electrodes) was recorded and SWA of the first hour of sleep was calculated. Abilities were significantly poorer in the very preterm compared to the term-group, particularly, if the tasks demands were high (p < .01). The score was positively correlated with sleep SWA in a cluster of 15 electrodes over frontal and negatively in a cluster of 14 electrodes over central brain regions after controlling for age at assessment and correcting for multiple comparisons. Within the frontal cluster, sleep SWA was higher in very preterm compared to term-born participants when controlling for executive function performance and age at assessment (p = .02). No difference in SWA between very preterm and term-born participants was found for the central cluster (p = .29). Our results demonstrate a local increase of sleep SWA over brain regions associated with executive processes in adolescents born very preterm compared to similarly performing term-born peers. Thus, sleep SWA seems to map the higher effort needed for executive function tasks in adolescents born very preterm.
Monitoring the formation of creative teaching abilities of teachers college graduates is extremely important. Creativity in the classroom is noways more relevant than ever. The main objectives of this work are: to study the general level of the formation of teachers college students’ creative abilities; to research the degree of development of individual creative components in teaching skills. Andreev's (1988) battery of psychodiagnostic techniques was applied to complete the stated tasks. Our conclusion was that a graduate of a teachers’ college represents a creative, cultivated, highly moral person with the intellectual level slightly below average, a low level of irritability, a high level of bureaucratic qualities, and a low to average level of personal-development ability.
Recently, ternary oxides have emerged as a new class of anode materials for lithium-ion battery due to their intrinsic advantages in accommodating volume expansion as well as improving the electrical conduction. This offers a new way to improve the cyclability of Ge-based anode which has been long plagued by capacity fading. Up to now, the studies on Ge-based ternary oxides anode are still scarce. Herein, we produced a novel Fe2GeO4 nanoparticles(NPs)/reduced graphene oxide (RGO) hybrid nanostructure and investigated its electrochemical performance in LIBs. During the cycling, a mixture in which Ge nanoparticles uniformly distributed in the matrix of Fe/Li2O formed. The Fe/Li2O matrix as well as the graphene can not only offer an elastic buffer but also provide a conductive medium for the whole anode. With the alleviated mechanical stress and the enhanced charge carrier transport, the hybrid anode exhibited a high reversible capacity of 980mAh/g for 175 cycles. Remarkable rate performance was also recorded. Our study shows that Fe2GeO4 NPs/RGO nanostructure could be a suitable candidate for high capacity lithium-ion battery.
The stabilities of olivine LiFePO4 and spinel LiMn2O4 in a LiPF6-based electrolyte were investigated by means of atomic absorption spectroscopy. At 85°C a significant increase in Mn/Fe dissolution was observed in comparison to 60°C stored cathode materials. However, the comparison indicates a much lower solubility of the LiFePO4 versus LiMn2O4. This result shows a new advantage of LiFePO4 as a promising alternative cathode.
In this work, Li/air batteries based on nonaqueous electrolytes were investigated in ambient conditions (with an oxygen partial pressure of 0.21atm and relative humidity of ∼20%). A heat-sealable polymer membrane was used as both an oxygen-diffusion membrane and as a moisture barrier for Li/air batteries. The membrane also can minimize the evaporation of the electrolyte from the batteries. Li/air batteries with this membrane can operate in ambient conditions for more than one month with a specific energy of 362Whkg−1, based on the total weight of the battery including its packaging. Among various carbon sources used in this work, Li/air batteries using Ketjenblack (KB) carbon-based air electrodes exhibited the highest specific energy. However, KB-based air electrodes expanded significantly and absorbed much more electrolyte than electrodes made from other carbon sources. The weight distribution of a typical Li/air battery using the KB-based air electrode was dominated by the electrolyte (∼70%). Lithium metal anodes and KB-carbon account for only 5.12% and 5.78% of the battery weight, respectively. We also found that only ∼20% of the mesopore volume of the air electrode was occupied by reaction products after discharge. To further improve the specific energy of the Li/air batteries, the microstructure of the carbon electrode needs to be further improved to absorb much less electrolyte while still holding significant amounts of reaction products.
Alternating copolymers (poly(1a-g-alt-VC)) of vinyl ethers with various methoxy oligo(ethyleneoxy)ethyl groups and vinylene carbonate (VC) were prepared, and the thermal and electrochemical properties of their polymer electrolytes with LiTFSI and interfacial stability between the polymer electrolyte and Li metal electrode were investigated. T g's increased linearly with salt contents, and decreased with an increase in the chain length of methoxy oligo(ethyleneoxy)ethyl groups in the vinyl ethers at constant salt concentration. The slopes of T g vs. [Li]/[O] were identical, independent of the polymer structure. The ionic conductivities of the polymer electrolytes increased with increasing the side-chain ethyleneoxy (EO) unit length of the vinyl ether unit in the alternating copolymers, and also their temperature dependences became relatively smaller in the polymer electrolytes having longer EO units in the vinyl ethers. The highest ionic conductivity, 1.2×10−4 S/cm at 30°C, was obtained in the alternating copolymer with a side-chain EO unit length of 23.5 in the vinyl ether unit. Ion transport coupled with the segmental motion of the polymer is dominant in these polymer electrolytes. Interfacial resistance increased gradually with contact time, indicative of the formation of passivation films on the Li metal electrode. These polymer electrolytes are thermally stable and have large electrochemical windows of use.
The electrochemical characteristics of Li x Ni y Co1−y O2 (0.5<y<0.9) prepared by a co-precipitation method were reported. Slow scan cyclic voltammetry (SSCV) and electrochemical impedance spectroscopy (EIS) were used to investigate the kinetic behavior of the composite electrodes. Kinetic data such as the Tafel slope and the charge-transfer resistance were determined based on the experimental results. An equivalent circuit model was proposed to simulate the impedance spectra and gave a good data fit. The present study also demonstrated that the kinetic data were composition-sensitive to varying lithium content and nickel content in the mixed oxide electrodes.
Dehydrogenated derivatives of corticosteroids are usually more effective than their precursors in treating diseases. In this study, the toxicity of seven water-miscible ionic liquid and three organic solvents to the biocatalyst Arthrobacter simplex UR016 was tested to evaluate the possibility of biodehydrogenation from 17α-hydroxy-16β-methyl-pregna-4,9(11)-diene-3,20-dione (HMPDD) to 17α-hydroxy-16β-methyl-pregna-1,4,9(11)-triene-3,20-dione (HMPTD) in an ionic liquid-containing system. Although most tested room temperature ionic liquids (RTILs) showed higher toxicities to A. simplex UR016 than organic solvents, bacterial growth was promoted in the presence of [EMIM](
Crystalline tungsten oxide mixtures, WO3–WO3·0.5H2O, prepared by microwave-assisted hydrothermal (MAH) synthesis at 180°C for various periods, show capacitive-like behavior at 200mVs−1 and C S ≈290Fg−1 at 25mVs−1 in 0.5M H2SO4 between −0.6 and 0.2V. Oxide rods can be obtained via the MAH process even when the synthesis time is only 0.75h while WO3·0.5H2O sheets with poor capacitive performances are obtained by a normal hydrothermal synthesis process at the same temperature for 24h. The aspect ratio of tungsten oxide rods is found to increase with prolonging the MAH time while all oxides consist of WO3 and WO3·0.5H2O. The oxide mixtures prepared by the MAH method with annealing in air at temperatures ≤400°C show promising performances for electrochemical capacitors (ECs). Due to the narrow working potential window of the oxide mixtures, an aqueous EC of the asymmetric type, consisting of a WO3–WO3·0.5H2O anode and a RuO2·xH2O cathode, with a potential window of 1.6V is demonstrated in this work, which shows the device energy and power densities of 23.4Wkg−1 and 5.2kWkg−1, respectively.
Metal-assisted chemical etching (MaCE) of metallurgical-grade silicon (MG-Si) has improved the purity of MG-Si (∼99%) to close to solar-grade (∼99.9999%) by removing metal impurities during the successful preparation of porous silicon nanowires (SiNWs). A new etching principle is proposed to explain the different levels of chemical reduction between various metal impurities with pore formation during etching. This model provides chemical insights into the relationship between dissolved metal ions and pores evolved during the formation of SiNWs.
With the increasing penetration of renewable energy, automatic generation control (AGC) capacity requirements will increase dramatically, becoming a challenging task that must be addressed. The rapid growth of electric vehicles (EVs) provides new approaches for the stable operation of power systems. Vehicle-to-grid (V2G) technology has the potential to provide frequency regulation (FR) services. Fully taking into account the advantages of EVs and battery energy storage stations (BESSs), i.e. rapid response and large instantaneous power, this paper presents a coordinated control strategy for large-scale EVs, BESSs and traditional FR resources involved in AGC. Response priorities and control strategies for the FR resources vary with different operating states. To verify the effectiveness of the proposed control strategy, dynamic simulations for EV/BESS to participate in AGC of a two-area interconnected power system are performed in the Matlab/Simulink program. The simulation results show that the proposed method can not only fully utilize the advantages of EV/BESS, but also achieve the coordination among different FR resources, thus improving the frequency stability and facilitating the integration of renewable energy.
Two-phase flow and transport of reactants and products in the cathode of a transparent proton exchange membrane fuel cell (PEMFC) are studied experimentally. Images of water formed inside the cathode gas channels are presented to explain the phenomenon of water flooding. Effects of air stoichiometry, temperature, air humidity and different characteristics of diffusion layers are discussed. The influence of hydrophobic and hydrophilic diffusion layers compared to standard carbon papers on water transport is investigated. Mathematical verification of a threshold current density corresponding to first appearance of liquid water at the membrane/cathode interface confirms the experimental results.
We design a novel polymer-graphite composite grid as the negative current collector for lead-acid batteries. With this novel grid, the negative active material (NAM) can deliver a specific capacity of 170 mAh g−1 at a discharge rate of 0.1 C. After that, we conduct structural optimization and surface treatment on the grid to improve its performance. Through the structural optimization, additional lead pastes can be loaded and the cycle stability of the battery is enhanced. By using the optimized grid, the weight of the negative current collector can be remarkably reduced by more than 50%. To handle the serious hydrogen evolution on the graphite surface and the unfavorable adhesion between graphite and NAM, fine PbSO4 particles are coated onto the surface of the graphite grids by chemical deposition. The cells employing the PbSO4-deposition grids exhibit excellent cycling stability as well as low polarization and then high Coulombic efficiency. We present here a possible mechanism that how PbSO4 deposits effectively enhance the performance of negative plates based on the testing results.
Lithium-intercalated graphite (LIG) is the most commonly used anode material for Li-ion batteries; however, the change in the electronic structure of LIG during battery operation is not fully understood. We have developed an in situ cell and a measurement method to elucidate this change using X-ray Raman scattering (XRS) spectroscopy. A confocal-like method enables the C K-edge spectrum of LIG alone to be extracted while avoiding the spectral overlap of carbon-containing components in the cell. In situ XRS and X-ray diffraction measurements are conducted simultaneously for LiC6, LiC12, and fully delithiated graphite during the delithiation process. The results indicate that the intensity of the π * peak of the XRS spectrum increases upon delithiation, and the σ * onset shifts to higher energy, which are consistent with prior spectroscopic studies on LIG. These results demonstrate that the in situ XRS method established in this study is useful to characterize the electronic properties of LIG during the operation of batteries.
The ever-increasing consumption of energy storage devices has pushed the scientific community to realize strategies toward organic electrodes with superior properties. This is owed to advantages such as economic viability and eco-friendliness. In this context, the family of conjugated dicarboxylates has emerged as an interesting candidate for the application as negative electrodes in advanced Li-ion batteries due to the revealed thermal stability, rate capability, high capacity and high cyclability. This work aims to rationalize the effects of small molecular modifications on the electrochemical properties of the terephthalate anode by means of first principles calculations. The crystal structure prediction of the investigated host compounds dilithium terephthalate (Li2TP) and diethyl terephthalate (Et2Li0TP) together with their crystal modification upon battery cycling enable us to calculate the potential profile of these materials. Distinct underlying mechanisms of the redox reactions were obtained where Li2TP comes with a disproportionation reaction while Et2Li0TP displays sequential redox reactions. This effect proved to be strongly correlated to the Li coordination number evolution upon the Li insertion into the host structures. Finally, the calculations of sublimation enthalpy inferred that polymerization techniques could easily be employed in Et2Li0TP as compared to Li2TP. Similar results are observed with methyl, propyl, and vinyl capped groups. That could be a strategy to enhance the properties of this compound placing it into the gallery of the new anode materials for state of art Li-batteries.
Single phase LiNi0.8−x Co0.1Mn0.1Cr x O2 (x =0, 0.01, 0.02, and 0.03) compounds have been prepared by fast co-precipitation and anneal method. Electrochemical tests show that the sample b, with 1% Cr content, exhibits the highest discharge capacity, enhanced rate ability and cycling property among all samples. From the combination of Rietveld refinements, ICP, EDAX and XPS studies, it is supposed that the electrochemical improvement may be related to the suppressed cation mixing degree and reduced surface concentration of Ni ions, caused by Cr substitution. However, excess Cr substitution could also result in the appearance of Cr6+ and Mn3+ ions, which are mainly responsible for the capacity fading of positive materials. Therefore, Cr substitution should be controlled in reasonable range.
Cultured human diploid fibroblasts and cultured rat granulosa cells were exposed to intermittent and continuous radiofrequency electromagnetic fields (RF-EMF) used in mobile phones, with different specific absorption rates (SAR) and different mobile-phone modulations. DNA strand breaks were determined by means of the alkaline and neutral comet assay. RF-EMF exposure (1800MHz; SAR 1.2 or 2W/kg; different modulations; during 4, 16 and 24h; intermittent 5min on/10min off or continuous wave) induced DNA single- and double-strand breaks. Effects occurred after 16h exposure in both cell types and after different mobile-phone modulations. The intermittent exposure showed a stronger effect in the comet assay than continuous exposure. Therefore we conclude that the induced DNA damage cannot be based on thermal effects.