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Pure LiFePO4 (LFP) thin films with different thicknesses are deposited at room temperature by a radio frequency (RF) magnetron-sputtering process. Ti foils with and without titanium nitride (TiN) coating as well as thermally oxidized Si wafers coated with Ti or TiN are used as substrates. In a subsequent annealing step, LiFePO4 thin films are crystallized at 500 °C. The interaction between Ti and LiFePO4 as well as between TiN and LiFePO4 is characterized by means of X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive X-ray analysis (EDX), secondary ion mass spectrometry (SIMS), cyclic voltammetry (CV) and galvanostatic measurements. A severe diffusion of Ti into LiFePO4 is found and leading to the formation of impurity phases which resulting in disturbing crystallization behaviour and rough surfaces. Moreover, 80 nm LiFePO4 thin films do not show the desired electrochemical characteristics when they are deposited on Ti foils directly. By using a TiN interlayer, the diffusion of Ti into LiFePO4 can be blocked resulting in smooth morphologies and improving crystallisation behaviour. Impurity phases do not develop and all samples exhibit the expected electrochemical characteristics. Therefore, TiN is a promising candidate for the use as a current collector in all-solid-state batteries with LiFePO4 electrodes.
A series of expanded graphitic materials are prepared from two different precursors: micrometric synthetic graphite and graphitized carbon nanofibers, and tested as anodes for sodium-ion batteries. The materials preparation involves the oxidation of the precursors followed by partial thermal reduction. Overall, the expanded synthetic graphite materials show better electrochemical performance as anode than the expanded graphite nanofibers, providing higher specific capacity, leading to lower capacity losses in the first discharge-charge cycle and exhibiting outstanding cycling stability. Specific capacities of ∼150mAhg−1 at 37mAg−1 and ∼110mAhg−1 at 100mAg−1 are attained, and up to 50% of the initial capacity at 19mAg−1 is kept at 372mAg−1. Unexpectedly, higher capacity losses are measured for the nanostructured electrodes by progressively increasing the current density. These differences are attributed to the lower surface area and porosity of expanded synthetic graphite materials which favors the formation of thinner and more stable SEI, thus reducing the electrode resistance and enhancing the accessibility of Na+ ions to surface oxygen-containing functional groups with the consequent increase of the surface capacity which was found to be the main contribution to the total specific capacity.
Gel polymer electrolyte films based on thermoplastic polyurethane (TPU)/poly(vinylidene fluoride) (PVdF) with and without in situ ceramic fillers (SiO2 and TiO2) are prepared by electrospinning 9wt% polymer solution at room temperature. The electrospun TPU–PVdF blending membrane with 3% in situ TiO2 shows a highest ionic conductivity of 4.8×10−3 Scm−1 with electrochemical stability up to 5.4V versus Li+/Li at room temperature and has a high tensile strength (8.7±0.3MPa) and % elongation at break (110.3±0.2). With the superior electrochemical and mechanical performance, it is very suitable for application in polymer lithium ion batteries.
Although many research efforts have been devoted to improving the electrochemical performance of ZnCo2O4, there is still a great need for a facile, low cost and time-saving method to synthesize ZnCo2O4. Herein, we first report a facile method to prepare mesoporous ZnCo2O4 with polypyrrole (PPy) coating (ZnCo2O4/PPy). The facile strategy involves a reflux method and a subsequent chemical polymerization method. The mesoporous ZnCo2O4/PPy shows an outstanding electrochemical performance. The discharge capacity of the ZnCo2O4/PPy is 615 mAh g−1 after 100 cycles at a current density of 0.1 A g−1. When the current density increases to 0.2 A g−1, the discharge capacity still retains 458 mAh g−1 after 100 cycles. The improved electrochemical performance is attributed to the coating of PPy layer, which acts as a conductive agent and buffer during charge/discharge. Our results demonstrate that the ZnCo2O4/PPy has potential as a high-energy anode material for lithium-ion batteries.
In recent years, the share of renewable energy sources (RES) in the electricity generation mix has been expanding rapidly. However, limited predictability of the RES poses challenges for traditional scheduling and dispatching mechanisms based on unit commitment (UC) and economic dispatch (ED). This paper presents an advanced UC-ED model to incorporate wind generators as RES-based units alongside conventional centralized generators. In the proposed UC-ED model, an imbalance cost is introduced reflecting the wind generation uncertainty along with the marginal generation cost. The proposed UC-ED model aims to utilize the flexibility of fleets of plug-in electric vehicles (PEVs) to optimally compensate for the wind generation uncertainty. A case study with 15 conventional units and 3 wind farms along with a fixed-sized PEV fleet demonstrates that shifting of PEV fleets charging at times of high wind availability realizes generation cost savings. Nevertheless, the operational cost saving incurred by controlled charging appears to diminish when dispatched wind energy becomes considerably larger than the charging energy of PEV fleets. Further analysis of the results reveals that the effectiveness of PEV control strategy in terms of CO2 emission reduction is strongly coupled with generation mix and the proposed control strategy is favored in cases where less pollutant-based plants like nuclear and hydro power are profoundly dominant.
Energy storage in PV cooling systems is desirable to supply on-site loads during solar outages. Current storage methods of such systems typically use battery storage to store surplus electricity generated by solar panels or coolth thermal energy storage (CTES) to store excess cooling capacity produced by an electric-driven chiller. This study compares three cooling system configurations – no energy storage, with a battery storage, and with a phase change CTES, for a residential building under the climate of Shanghai, Madrid and Brisbane. System simulation of each configuration was conducted using TRNSYS. A CTES component was programmed externally using effectiveness-NTU method. Both energy storage methods were compared with regard to energy change during a summer day, power consumption and primary energy saving ratio (PESR) during the cooling season. In addition, performance of a single battery and a single CTES were evaluated under various operational conditions. The results showed good energy performance of both storage cases. The PESR of battery case and coolth storage case were 2.8 times and 1.9 times higher than that of a reference case with no energy storage.
A homogeneous nanocomposite of SnSe and carbon black, denoted as SnSe/C nanocomposite, was fabricated by high energy ball milling and empolyed as a high performance anode material for both sodium-ion batteries and lithium-ion batteries. The X-ray diffraction patterns, scanning electron microscopy and transmission electron microscopy observations confirmed that SnSe in SnSe/C nanocomposite was homogeneously distributed within carbon black. The nanocomposite anode exhibited enhanced electrochemical performances including a high capacity, long cycling behavior and good rate performance in both sodium-ion batteries (SIBs) and lithium-ion batteries (LIBs). In SIBs, an initial capacitiy of 748.5mAhg−1 was obtained and was maintained well on cycling (324.9mAhg−1 at a high current density of 500mAg−1 in the 200 th cycle) with 72.5% retention of second cycle capacity (447.7mAhg−1). In LIBs, high initial capacities of approximately 1097.6mAhg−1 was obtained, and this reduced to 633.1mAhg−1 after 100cycles at 500mAg−1.
The electrochemical performances of fluorinated graphite have been improved by coating a uniform carbon layer on commercial CF x (x =1) powder used as cathode material in lithium battery. In comparison with the cell using un-coated CF x as cathode, the cell using carbon coated CF x cathode has a higher energy density and higher power density, particularly at higher discharge current rates (1C above). This is because the conductive carbon coating provides the exterior connectivity between particles for facile electron conduction, resulting in high rate performance.
Spinel Li4Ti5O12 known as a “zero-strain” anode material for Li-ion battery has attracted much attention because of its superior safety and stability. Herein, we report a novel H2O2-assisted one-step hydrothermal method to synthesize different ratio Li4Ti5O12/TiO2 composites with the same amount of raw materials. For the first time, Li4Ti5O12 was prepared directly from commercial titania with the presence of H2O2, and different proportion Li4Ti5O12/TiO2 composites were fabricated only by adjusting the amount of H2O2. The reaction mechanism of the novel H2O2-assisted method was clearly investigated, and H2O2 plays a crucial role in the formation of intermediate Li1.81H0.19Ti2O5·2H2O. Further, the electrochemical performance of different ratio Li4Ti5O12/TiO2 composites have been investigated. This facile method is also applicable for the preparation of Na2Ti6O13/TiO2 material, and provides us the new way to fabricate composite materials.
Continuous free-standing Carbon Nanotubes (CNTs)/Titanium oxide (TiO2) composite films were fabricated in a vertical CVD gas flow reactor with water sealing by the One-Step Chemical Vapor Deposition (CVD) approach. The composite films consist of multiple layers of conductive carbon nanotube networks with titanium oxide nanoparticles decorating on carbon nanotube surface. The as-synthesized flexible and transferrable composite films show excellent electrochemical properties, when the content of tetrabutyl titanate is 19.0wt.%, which can be promising as binder-free anodes for Lithium-Ion Battery (LIB) applications. It demonstrates remarkably high rate capacity of 150mAhg−1, as well as excellent high rate cyclic stability over 500 cycles (current density of 3000mAg−1). Such observations can be attributed to the relatively larger surface area and pore volume comparing with pristine CNT films. Great potentials of CNTs/TiO2 composite films for large-scale production and application in energy devices were shown.
1M NaClO4 and 1M NaPF6 electrolyte solutions in ethylene carbonate–dimethyl carbonate solvent mixture (1:1 by volume) were studied for the possible application in electrical double layer capacitors (EDLCs) with carbide-derived carbon electrodes (synthesized from Mo2C). Two- and three-electrode test cells were electrochemically characterized by using cyclic voltammetry, constant current charge/discharge and electrochemical impedance spectroscopy methods. Region of ideal polarizability, values of series capacitance, high-frequency resistance, time constants, etc. have been established. Based on the specific energy and power calculations, and other characteristics, it was found that the Na-salts based EDLC test cells have similar electrochemical behavior compared to LiPF6 and LiClO4 based systems that have been studied earlier. The studied Na-salts based electrolytes are potential candidates for EDLCs, however, future improvement of the cyclability is inevitable to achieve long-lasting high performance.
With increases of display resolution and graphical quality demands, global illumination techniques are sought after to meet such demands. However, global illumination algorithms have a long processing time on mobile devices, such as smartphones or tablet PCs. Besides the performance issue, the algorithms consume a large amount of battery-powered energy. The performance and energy consumption have a trade-off relationship. The dynamic voltage and frequency scaling (DVFS) algorithms control the balance between the performance and the energy consumption by adjusting the GPU and CPU’s frequencies. To improve the performance of the global illumination algorithm and reduce the high energy consumption of the current DVFS algorithm, we suggest new algorithms with new metrics for estimating the amount of workload for GPUs as well as their memory workload. Using our new DVFS algorithms, we increase the energy efficiency, the performance per watt, of a global illumination algorithm by 33.59% in comparison to a conventional general-purpose DVFS algorithm, without modifying the underlying algorithm core.
In this work, sodium doped LiVO3 cathode is proposed to achieve enhanced cycling performance for lithium ion battery (LIB) application. LixNa2-xV2O6 (x = 2, 1.4, 1, 0) compounds have been prepared and characterized, and X-ray diffraction patterns confirmed the successful Na doping with various amounts in the LiVO3. The electrochemical performances of the various Na doped compounds LiVO3, Li1.4Na0.6V2O6, LiNaV2O6, and NaVO3 are evaluated by cyclic voltammetry, galvanostatic charge/discharge and electrochemical impedance spectroscopy. The results reveal that Na-doping amount strongly affects the electrochemical performance, and LiNaV2O6 (x = 1) is considered as the optimized Na doped compound for LIB cathodes. The LiNaV2O6 cathode displays enhanced cycling and rate performances as a specific capacity of 193 mAh g−1 at 0.5 C after 100 cycles is delivered. The enhanced performance is explained that the doping of Na can provide good channels and increase Li+ diffusion coefficient for lithium ion intercalation/deintercalation.
High-voltage stability of LiBF4 - propylene carbonate solutions in intermediate concentration range is studied by means of cyclic voltammetry, galvanostatic cycling and X-ray photoelectron spectroscopy using LiCoPO4 and LiNi0.5Mn1.5O4 cathode materials. Coulombic efficiency improves with increasing salt-to-solvent molar ratio from 1:12 to 1:4 (∼0.8 m–2.5 m solutions), reaching 98% at 1C charge/discharge rate for 1:4 electrolyte upon cycling of LiNi0.5Mn1.5O4 up to 5 V vs. Li/Li+. The same positive trend is observed for discharge capacities, cycling stability and capacity scattering for both high-voltage cathode materials. X-ray photoelectron spectroscopy of the electrodes studied after cycling in solutions of different concentrations does not reveal any drastic difference in surface composition. Interface pre-formation experiment shows that the presence of the interface layer formed at semi-concentrated 1:4 electrolyte does not have a major impact on the electrochemical properties of the dilute solution. We assume that the enhanced oxidation stability of the concentrated solutions itself is a reason of improving the electrochemical performance rather than the cathode-electrolyte interface properties.
Malnutrition and cachexia have a negative impact on the course of treatment in patients with head and neck squamous cell carcinoma (HNSCC). Good evidence exists for the practical use of the bioelectrical impedance analysis (BIA) parameter phase angle (PA) for the evaluation of nutritional and overall health status in cancer patients. In the present study, two hypotheses were tested: that PA can distinguish between malnutrition and cachexia; in non-cachectic patients, pre-treatment PA is predictive for cachexia development during (chemo)radiation.
By varying Co:Sb molar ratio, crystalline CoSb2O4 was synthesized through surfactant free hydrothermal method. The tetragonal crystal structure and phase composition of cobalt antimonate were obtained through XRD Rietveld refinement method. CoSb2O4 exhibits a direct band gap of 2.89 eV was computed using First-principle density functional theory (DFT) calculations. Here, the Fermi energy level is upshifted to conduction band region, representing the n-type behaviour of the CoSb2O4 unit cell. The oxidation state of +2 and + 3 of Co was identified through X-ray photoelectron spectroscopy analysis (XPS). Formation of submicron size, rod shape particles was confirmed by Transmission electron microscopic (TEM) images. Cyclic voltammogram exhibits a specific capacitance of 598 F g−1 at 2 mV s−1 in 1 M KOH. More importantly, Galvanostatic charge-discharge analysis (GCD) delivered the specific capacitance of 382 F g−1 at 1 mA cm−2. For practical application, an asymmetric supercapacitor is constructed using Ni3(Fe(CN)6)2(H2O) as a positive electrode and synthesized one-dimensional CoSb2O4 as a negative electrode, which offered a maximum specific capacitance of 279 Fg-1 at 1 mV s−1. Cycling stability of the fabricated device demonstrated the retention of almost 100% and hence depicts its promising nature as an efficient electrode for supercapacitor application.
A nanostructured composite with overall atomic composition Ni0.14Sn0.17Si0.32Al0.037C0.346 has been prepared combining powder metallurgy and mechanical milling techniques for being used as anode material in Li-ion battery. Chemical and structural properties of the nanocomposite have been determined by X-ray diffraction (XRD), 119Sn Transmission Mössbauer Spectroscopy (TMS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The composite consists of Si particles with typical size ∼150nm embedded in a poorly crystallized and complex multielemental matrix. The matrix is composed mostly by Ni3.4Sn4, and disordered carbon. Electrochemical evaluation shows a high reversible capacity of 920mAhg−1, with reasonable reversible capacity retention (∼0.1% loss/cycle) over 280 cycles.
To improve the cycling stability and rate performance of SnO2–based anode materials applied in lithium ions batteries (LIBs), SnO2/graphene oxide (SnO2/GO) composite was synthesized by hydrothermal method. The SnO2/GO composite material exhibits much more excellent lithium ions storage capacity and cycling stability. The reversible capacity is 612.2 mAhg−1 with the coulombic efficiency of 98.8%, after 100 cycles. Especially, at a high discharge-charge current density (1000 mAg−1), the SnO2/GO composite showed an outstanding structure stability and rate performance (204.2 mAhg−1). Such excellent performance could be attributed to the existence of GO. With the assistance of GO, the composite material achieves more stable structure and high electron conductivity.
Developing devices and related materials for storing and producing electricity is a key issue to meet the global energy demand. Low-cost and high-performance energy-storage devices are important for sustainable energy utilization. Recently, lithium-ion battery (LIB) is emerging as a promising power source for high-performance electronics. However, their technological drawbacks have hindered the development of LIB with improved specific capacity, stable cyclic and coulombic efficiency for portable electronics application, due to the lack of availability of reliable electrode materials that provided superior electrochemical properties. As a solution to this problem, we herein demonstrated two types of few-layered graphene produced by Fenton reaction (FG) and Hummers method (HG) used for the fabrication of electrodes on flexi copper and aluminum foils in two different ways. Lithium iron phosphate (LiFePO4 or LFP) mixed with super-P carbon black (SP) and fabricated cathode, FG and HG, respectively, blended with SP and fabricated two anodes, by carefully balancing the cell composition of the anode and cathode. An optimal cell performance in terms of specific capacity and stable cyclability depends on the fabrication method of electrodes and their chemical composition. The FG electrodes showed a specific capacity of 186 mAh g−1 at 150 mA g−1 charge/discharge (C/D) current rate while HG showed a specific capacity of 195mAh g−1 at same C/D rate without capacity decay during 30 cycles and an excellent cycling stability was also observed when HG was used in cathode with SP in the same ratio at 150, 300 and 450 mA g−1 C/D rate in full LIB.
A facile procedure are developed to fabricate graphene-bonded and -enwrapped mesoporous anatase TiO2 microspheres (GMTMs) using graphene oxide (GO) and titanium glycolate microspheres (TGMs) as precursors without using any cross-linking reagents. Highly nanoporous TiO2 spheres are generated via in situ hydrolysis of the TGMs and then wrapped by GO nanosheets over their surface through covalent linkage during a reflux process. After hydrothermal treatment and calcination in an Ar atmosphere, the crystallization of TiO2 and the reduction of GO is significantly increased simultaneously. Electrochemical performance of the mesoporous TiO2 microspheres (MTMs) enwrapped with chemically-bonded graphene is greatly improved in terms of specific capacity, rate capability and cycle stability. The composite material shows a discharge capacity of 170 mA h g−1 at the 10 C rate, which is much higher than that of the pristine TiO2 microspheres (116 mA h g−1).
Glutathione peroxidase (GPx) is a key enzyme of cellular detoxification systems that defend cells against reactive oxygen species. Knowledge of the complement of GPx in shrimp is essential to understanding regulation and detoxification mechanisms of environmental stress. In this study, we expressed GPx from white shrimp Litopenaeus vannamei in Escherichia coli, and then characterized the purified recombinant enzyme with respect to the effects of pH, temperature on its catalytic activity. Quantitative real-time PCR and western blot analysis were carried out to investigate the expression patterns of GPx in shrimp hepatopancreas exposed to Cd stress. A statistically significant increase in expression of GPx mRNA and protein was observed in the Cd stress at 24 h. By contrast, western blot showed a significant up-regulation in GPx protein expression at 12 h exposed pH stress (5.6 and 9.3, respectively). These results suggest that L. vannamei GPx expression was modulated by Cd and pH stress and may play an important role in detoxification of xenobiotics and antioxidant defense. We conclude that GPx could be used as biomarkers of Cd and pH stress in aquatic environment for the studied species.
Magnesium and its alloys are prone to corrosion upon exposure to atmosphere thus are usually protected by using a pretreatment before being employed. The use of ionic liquids (ILs) has emerged as a novel chemical in corrosion protection of reactive metals such as lithium and magnesium. This paper reviews the use of ILs in the corrosion protection of magnesium and aluminium with respect to a range of IL chemistries. Emphasis has also been placed on characterisation of the passivating films using various techniques, as well as proposed mechanisms for film formation. This review highlights that there is still much research needed to understand how to generate robust passivating films on reactive metal surfaces in the presence of ILs.
Sodium-ion batteries (SIBs) are considered as a promising candidate to lithium-ion batteries (LIBs) owing to the inexpensive and abundant sodium reserves. However, the application of anode materials for SIBs still confront rapid capacity fading and undesirable rate capability. Here we simultaneously grow ultrafine ZnSe nanoparticles on the inner walls and the outer surface of hollow carbon nanospheres (ZnSe@HCNs), giving a unique hierarchical hybrid nanostructure that can sustain a capacity of 361.9 mAh g−1 at 1 A g−1 over 1000 cycles and 266.5 mAh g−1 at 20 A g−1. Our investigations indicate that the sodium storage mechanism of ZnSe@HCNs electrodes is a mixture of alloying and conversion reactions, where ZnSe converts to Na2Se and NaZn13 through a series of intermediate compounds. Also, a full cell is constructed from our designed ZnSe@HCNs anode and Na3V2(PO4)3 cathode. It delivers a reversible discharge capacity of about 313.1 mAh g−1 after 100 cycles at 0.5 A g−1 with high Columbic efficiency over 98.2%. The outstanding sodium storage of as-prepared ZnSe@HCNs is attributed to the confinement of ZnSe structural changes both inside/outside of hollow nanospheres during the sodiation/desodiation processes. Our work offers a promising design to enable high-power-density electrodes for the various battery systems.