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We investigate the electrochemical side reactions that occur during the cyclic lithiation/delithiation of sputter-deposited Li x V2O5 films. For this purpose, the mass change of Li x V2O5 films during lithiation/delithiation is measured by quartz crystal microgravimetry, while the electrical charge that is flowing during this reaction is measured by cyclic voltammetry. A time-resolved evaluation of the measurement data, in combination with an advanced type of data processing, finally allows us to calculate time-resolved quantitative mass spectra. These spectra provide information about the chemical species that take part during the electrochemical reactions. Based on this technique, we study the electrochemical side reactions between the Li x V2O5 and the corresponding liquid electrolyte, i.e. we investigate the time-resolved formation of the solid electrolyte interface (SEI) layer during long term cycling. We are able to identify several chemical species that are formed during cycling and moreover, we identify three different stages of SEI formation.
Co2+-doped Li4Ti5O12 (LTO) in the form of Li4Ti5-xCoxO12 (x=0, 0.10, 0.15, 0.20) is prepared using a facile hydrothermal method. The doping of Co2+ leads to a decrease of the charge transfer resistance and improvement of the lithium ion diffusion coefficient. The as-prepared samples, Li4Ti5-xCoxO12 (x=0.15) exhibits the best cycling stability and rate capability as anode material for lithium ion batteries, which delivers the initial specific capacity of 168.3, 163, 159, 156.4, 145.9, 140.4, 130.9 and 112.6mAhg−1 at 1, 2, 5, 10, 15, 20, 30 and 50C (1C=175mAhg−1) rate in the voltage range of 1.0-2.5V respectively, and a discharge capacity of 109.3mAhg−1 after 1000 cycles at 50C. In addition, it keeps a discharge capacity of 150.8mAhg−1 (95.1% retention) at 5C even after 3000 cycles. Therefore, Co2+ doping technique provides an effective approach to improve electrochemical performances of LTO.
Lithium–oxygen (Li–O2) battery is considered as one of the most promising technologies among various electrochemical energy systems, since it can offer much higher theoretical energy density than the conventional lithium-ion battery. However, a high voltage gap between charge and discharge significantly limits the round-trip efficiency and cycle stability of Li–O2 batteries. In the present work, mesoporous Co3O4 is simply prepared and studied as a catalyst in Li–O2 cells. The Co3O4 nanoparticles possesses a high specific surface area and a spinel crystalline structure. Cyclic voltammetries demonstrate that mesoporous Co3O4 catalyst enhances the kinetics for either oxygen reduction reaction (ORR) or oxygen evolution reaction (OER). Such excellent catalytic performance of Co3O4 could be associated with its larger surface area and 3D ordered mesoporous structure. The electrode with mesoporous Co3O4 exhibits a higher discharge capacity and lowers the over-potential for discharge process, compared with the pure carbon electrode. In Li–O2 cells, the Co3O4 cathodes show enhanced electrochemical performances, including a high round-trip efficiency and a prolonged cycle life. More than 65 stable cycles are observed with a Co3O4-catalyzed electrode, which could be attributed to the low recharge voltage, at which main side reactions due to decomposition of TEGDME-based electrolyte can be suppressed.
Graphene/Si multilayer structures were constructed through a repeated process of filtering liquid-phase exfoliated graphene film and the subsequent coating of amorphous Si film via plasma-enhanced chemical vapor deposition (PECVD) method. The multilayer heterogeneous structure films, directly fabricated on copper current collectors, were used as anodes for rechargeable lithium half-cells and full-cells without adding any polymer binder or conductive additives. The half cells based on the new anodes could easily achieve a capacity almost four times higher than the theoretical value of graphite even after 30 cycles' charging/discharging. It also demonstrated improved capacity retention compared to those of pure Si film-based anodes. Furthermore, full cells composed of the graphene/Si multilayer structure anodes and commercially available LiNi1/3Mn1/3Co1/3O2 cathodes were also assembled. Initial results showed good electrochemical performance comparable to that of commercially available rechargeable LIBs. Our prepared multilayer structures, taking advantage of the long cycle life of carbon and the high lithium-storage capacity of Si, provided a promising research platform that may eventually lead to an optimized anode structure for advanced rechargeable LIBs.
Calcium phosphate was used for surface modification of spherical nickel hydroxide to improve its high temperature performance at the first time due to its low cost. The Ca3(PO4)2 and Co(OH)2 coated nickel hydroxides were prepared by precipitation of Ca3(PO4)2 on the surface of spherical nickel hydroxide, followed by precipitation of Co(OH)2 on its surface. The optimum coating content of calcium was around 2% (atomic concentration) to obtain high discharge capacity both at 25 and 60°C. It was shown that the discharge capacity of nickel hydroxide at higher temperatures was improved by coating of Ca3(PO4)2 and cobalt hydroxide. The high temperature performances of the sealed AA-sized nickel–metal hydride (Ni–MH) batteries using Ca/Co coated nickel hydroxide as positive electrodes were carried out, showing much better than those using uncoated or only Co(OH)2 coated nickel hydroxide electrodes. The charge acceptance of the battery using 2% Ca and 2% Co coated nickel hydroxide reached 81% at 60°C, where the charge acceptances for uncoated and only Co(OH)2 coated nickel hydroxide were only 42 and 48%, respectively. It has shown that the Ca/Co coating is an effective way to improve the high temperature performance of nickel hydroxide for nickel–metal hydride batteries. It is a promising cathode material of Ni–MH batteries for EV applications due to the cost.
The electrodepositions of Sn(II) and Sb(III) were studied in the [EMIm]BF4 ionic liquid at ambient temperature. Linear sweep voltammetry (LSV) results indicated that the reductions of Sn(II) and Sb(III) on Pt electrode are electrochemically irreversible. The diffusion coefficients of Sn(II) and Sb(III) in the ionic liquid electrolyte were determined in terms of the LSV data. Tin and antimony ions form simpler Sn(II) chlorocomplex species and higher Sb(III) chlorocomplexes, respectively present in the ionic liquid electrolyte. Energy dispersive X-ray spectroscopy (EDX) analysis revealed that tin and antimony alloys can be electroplated in the ionic liquid electrolyte.
Thin and thick metal hydride (MH) electrodes used in air–MH batteries were evaluated with respect to electrochemical performances. The influence of electrode thickness on the discharge capacity, rate capability, charge and discharge voltages was investigated as well as the effect of MH packing density within electrodes on the electrode performances was also examined. The mass transport within the porous electrode was found to be the rate limiting step with increasing electrode thickness. The power output could be increased by either using thin electrodes or decreasing electrode density. This was, however, done at the expense of the energy density of the cell.
In the work, hierarchical SnS2/SnO2 composites have been successfully synthesized by a facile one-step solvothermal method. It is found that the basic nature of the solution plays a crucial role in ascertaining the phase and structures of the Sn-based products. And compared with plate-like SnS2 nanoparticles fabricated in deionized water (DI w), the sphere-like SnS2/SnO2 composites obtained in anhydrous ethanol (AE) exhibit excellent electrochemical performances as anode material for lithium-ion batteries (LIBs). The discharge capacity of SnS2/SnO2 electrode retains 588.15mAhg−1 at 100mAg−1 after 50 cycles, and the discharge capacity of the electrode can still stably reserve 559.16mAhg−1 even at 800mAg−1, demonstrating a significantly increased cycling reversibility and structural stability compared to the bare SnS2. The sphere-like SnS2/SnO2 structure are assembled by nanoparticles, which can shorten the lithium-ions/electrons pathways, the hierarchical structure of SnS2/SnO2 composites can accommodate the large volume variation. The charge/discharge performance of the SnS2/SnO2 composites can also be enhanced by the synergy effects of SnS2 and SnO2.
An all solid-state rechargeable lithium battery was successfully fabricated using a ceramic electrolyte and a thin film technique. A polymer-modified sol–gel method was applied in order to prepare the electrode-coated ceramic electrolyte. Li4Ti5O12 known for its outstanding electrochemical performances and the partially crystallized glass ceramics, LiTi2(PO4)3–AlPO4 were adopted as electrode and electrolyte materials, respectively. The all solid-state battery cell constructed with lithium metal, PMMA buffer, and electrode-coated ceramic electrolyte was electrochemically evaluated with ac impedance, cyclic voltammetry, and discharge–charge test. The impedance of the interface between Li4Ti5O12 film and the solid electrolyte showed a relatively low resistance of ∼110Ωcm−2 at 1.60V. Highly reversible sharp redox peaks were observed at around 1.55V from cyclic voltammograms, and these were still clear even at a high scan rate of 3mVs−1, indicating a fast electrochemical response. A charge–discharge experiment showed an excellent reversibility of the cell but a relatively smaller discharge capacity of 100.49mAhg−1 at C/5 than theoretical one of 175mAhg−1. This may be due to formation of an interlayer at the interface, which may be caused by chemical reaction between Li4Ti5O12 and the ceramic electrolyte during a firing step during preparation. In spite of the undesirable side-reaction, the ceramic electrolyte was successfully applied to the solid-state rechargeable lithium battery by means of a thin film technique using the polymer-modified sol–gel method, through increasing the interfacial contact area, i.e. reducing the interfacial resistance.
Nanotechnology is an enabling technology that provides an extensive range of resources to resolve the energy-related problems, as the developing components and appliances are smaller than 100nm they provide the new ways to catch, store and exchange energy. Every day, the sun shines a huge amount of energy which is generated through a process of nuclear fusion. Even the sun radiates more energy in one second than people have practiced since the beginning of time. It has been noted that the technical potential of solar energy all over the world is many times larger than the current total primary energy demanded. In this study, the solar harvesting technology with the help of nano-materials has been thoroughly studied. The different types of modern solar collecting technologies that use the nano-materials effectively and successfully have been discussed. Among a number of devices, the solar collector, the fuel cell, photocatalysis and solar photovoltaic have used the nanomaterials to increase the efficiency. It is found that by using nanomaterials the incident radiation can be increased by 9 times while the efficiency of the solar collector is 10% higher compared to that of a conventional flat plate solar collector. The generation ways solar cell technologies have been also discussed here. At the end of this article, few challenges in using nanotechnology are also addressed in detail.
A kind of nonfilling polyaniline coating of sulfur/acetylene black composite is prepared via a facile and eco-friendly approach in consider of the different solubility of sulfur in the liquid phases and at the proper temperature. Acetylene black particles with the particle size of 50 nm are partially infiltrated with sulfur, just the outer surface are coated with polyaniline shell. When using as a cathode material for lithium sulfur batteries, it exhibits significantly enhanced rate capability (initial capacity of 810 mAh/g at 2C, 486 mAh/g at 5C), and rate stability after 500 cycles (>351 mAh/g at 5C). This considerable electrochemical performance could be attributed to the highly uniform distribution of sulfur in the nanopores of the conductive acetylene black and the physical isolation of the sulfur with electrolyte by conductive polyaniline. This renders it to be a promising candidate for practical application in lithium sulfur batteries.
Sodium-ion batteries (SIBs) are establishing themselves as a low-cost alternative to the widespread lithium-ion technology, a trend that is exemplified by the use of aluminium as anode current collector. In order to be in line with this philosophy, environmentally friendly, abundant and cheap materials need to be used in order to provide a complementary rather than competing battery technology other than lithium-ion. With the same scope in mind, herein we present the structural and electrochemical characterization of P2-type NaxMg0.11Mn0.89O2 material to demonstrate the effectiveness of Mg-doping for the development of future layered cathode materials. Of particular interest is the effect on the long-term cyclability (200 cycles), which has not been reported, yet. As shown in the manuscript, a Mg content as low as 11% in the MO2 layer leads to a smoothing of the potential profile, very high coulombic efficiencies exceeding 99.5% at 12mAg−1 and a stable long-term cycling behaviour.
A simple, sensitive, and reliable method for the voltammetric determination of roxithromycin (RM) at the surface of the fabricated poly(3,4-ethylenedioxythiophene) (PEDOT) modified Au electrode has been successfully developed. The electrochemical behavior of RM at the surface of the modified electrode was investigated by cyclic voltammetry and differential pulse voltammetry. The influence of experimental parameters including PEDOT modified various solid electrodes, supporting electrolytes, nano-modified materials, buffer solutions, pH values and scan rates on the response of RM were studied. Under optimal conditions, the as-prepared modified electrode can be employed to the quantification of RM with a linear range covering from 0.08 to 20μM, a high sensitivity of 0.9921μAμM−1, and a low detection limit of 0.0267μM. Furthermore, the proposed modified electrode displayed high stability, good reproducibility and high sensitivity. The voltammetric determination of RM content in its capsule samples by using the as-prepared modified electrode also showed a satisfactory result with the good recovery in the range from 98.9% to 102.0%. The good result on the voltammetric determination of RM also indicated that the as-fabricated PEDOT modified Au electrode will be a good candidate for the electrochemical determination and analysis of other macrolide antibiotics.
Sustainable energy is becoming of increasing concern world-wide. The rapid growth of global climate changes along with the fear of energy supply shortage is creating a large consensus about the potential benefits of a hydrogen economy coming from renewable energy sources. The interesting perspectives are over-shadowed by uncertainties about the development of key technologies, such as renewable energy sources, advanced production processes, fuel cells, metal hydrides, nanostructures, standards and codes, and so on. The availability of critical technologies can create a base for the start of the hydrogen economy, as a fuel and energy carrier alternative to the current fossil resources. This paper will explore the rationale for such a revolution in the energy sector, will describe the state-of-the-art of major related technologies (fuel cell, storage systems, fuel cell vehicles) and current niche applications, and will sketch scientific and technological challenges and recommendations for research and development (R&D) initiatives to accelerate the pace for the widespread introduction of a hydrogen economy.
Two stable modifications of A3V2(PO4)3 (A = Na or Li) were synthesized by citric acid assisted modified sol–gel synthesis. The obtained samples were phase pure Li3V2(PO4)3 and Na3V2(PO4)3 materials embedded in a carbon matrix. The samples were tested as half cells against lithium or sodium metal. Both samples delivered about 90 mAh g−1 at a C/10 cycling rate. The change of vanadium oxidation state and changes in the local environment of redox center for both materials were probed by in-situ X-ray absorption spectroscopy. Oxidation state of vanadium was determined by energy shift of the absorption edge. The reversible change of valence from trivalent to tetravalent oxidation state was determined in the potential window used in our experiments. Small reversible changes in the interatomic distances due to the relaxation of the structure in the process of alkali metal extraction and insertion were observed. Local environment (vanadium–oxygen bond distances) after 1st cycle were found to be the same as in the starting material. Both structures have been found very rigid without significant changes during alkali metal extraction.
A selection of interesting papers that were published in the two months before our press date in major journals most likely to report significant results in neurobiology.
Nanocrystalline and amorphous NdMg12-type NdMg11Ni + x wt% Ni (x = 100, 200) alloys were successfully prepared through ball milling (BM). The microstructures and electrochemical properties were systematically studied to get a more comprehensive understanding of the sample alloys. The maximum discharging capacity could be obtained at only two cycles, indicating that as-milled alloys have superior activation capability. The more the Ni content, the better the electrochemical properties of the as-milled samples. To be specific, the discharge capacities of x = 100 and x = 200 (BM 20 h) samples are 128.2 and 1030.6 mAh/g at 60 mAh/g current density, respectively, revealing that enhancement of Ni content could significantly improve the discharging capacities of the samples. Additionally, milling duration obviously influences the electrochemical properties of the samples. The discharging capacity always rises with milling duration prolonging for the x = 100 sample, but that of the (x = 200) sample shows a trend of first augment and then decrease. The cycling stability of the (x = 100) alloy clearly decreases with extending milling duration, whereas that of the (x = 200) alloy first declines and then augments under the same conditions. In addition, the high rate discharge (HRD) abilities of the sample display the maximal values as milling duration changes. The HRD (HRD = C300/C60 × 100%) values of the as-milled alloys (x = 100, 200) are 80.24% and 85.17%, respectively.
Case managers struggle when arranging patient care services about which they know very little, especially when the patient is particularly vulnerable. Arranging air medical transport, for example, can be an exercise fraught with risks. The following questions will help you coordinate a smooth transport and help ensure the patient is cared for by qualified health care professionals in a safety-conscious environment.
Battery active materials are evaluated using numerous material characterization techniques for fundamental understanding, comparative analysis during research and development, and for quality control during manufacturing. Electrochemical properties of the active materials also need to be investigated and validated, and this analysis is very time and material intensive generally requiring electrode fabrication, cell assembly and cell cycling. In addition, evaluating active materials electrochemically in battery cells can be complicated by the electrode microstructure and the contributions of other components within the cell that are not the active materials. In this report, an active material characterization method is demonstrated to provide electrochemical insights for lithium-ion cathode materials by dispersing them into aqueous electrolyte and flowing through an electrochemical reaction cell. This method requires very little active material and time to conduct the measurements, typically requiring under 0.1 grams of material and less than 10minutes. The measured resistance from this technique provides insights into the electrochemical performance of the active material and generally correlates to the rate capability. This measured resistance is insensitive to other electrode components or electrode microstructure because there is no electrode fabrication step. LiFePO4 was chosen as a commercial material for initial demonstration of the technique.
Capacitive deionization (CDI) is an emerging technology for the facile removal of charged ionic species from aqueous solutions, and is currently being widely explored for water desalination applications. The technology is based on ion electrosorption at the surface of a pair of electrically charged electrodes, commonly composed of highly porous carbon materials. The CDI community has grown exponentially over the past decade, driving tremendous advances via new cell architectures and system designs, the implementation of ion exchange membranes, and alternative concepts such as flowable carbon electrodes and hybrid systems employing a Faradaic (battery) electrode. Also, vast improvements have been made towards unraveling the complex processes inherent to interfacial electrochemistry, including the modelling of kinetic and equilibrium aspects of the desalination process. In our perspective, we critically review and evaluate the current state-of-the-art of CDI technology and provide definitions and performance metric nomenclature in an effort to unify the fast-growing CDI community. We also provide an outlook on the emerging trends in CDI and propose future research and development directions.
The demand for high-performance energy storage devices such as supercapacitors and lithium-ion batteries has been increasing to meet the application requirements of renewable energy systems. Here, high energy density aqueous asymmetric supercapacitor (ASC) is assembled based on carbon nanofibers (CNF) network positive electrode and tungsten trioxide (WO3) nanorod bundles negative electrode. Polyaniline-based CNF are prepared by direct carbonization of polyaniline nanofibers. WO3 nanorod bundles are synthesized via a simple sodium chloride assisted hydrothermal process. The CNF//WO3 ASC device operates with a voltage of 1.6V and achieved a high energy density of 35.3 Wh kg−1 at a power density of 314Wkg−1. Furthermore, the device shows an excellent cycling performance with capacitance retention of 88% after 1000 cycles.
Molybdenum disulfide/nitrogen-doped carbon nanocomposite can afford high capacity, good rate capability and cycling stability in lithium ion batteries owing to the synergistic effect from these two components. Structure of the material has a great impact on the performance as well. In this work, MoS2/nitrogen-doped carbon (MoS2/C) composites have been developed by manipulating the nano-featured polypyrrole templates to guide and confine their growth. They are formed via a simple hydrothermal process combined with a subsequent annealing process. The MoS2/nitrogen-doped carbon nanotubes (MoS2/CNT) composite with 76% of MoS2 exhibits an excellent performance including a high capacity of 1232 mAh g−1 at a current density of 0.1 A g−1, outstanding rate capability (947 mAh g−1 at 2 A g−1), and good cycling stability with 754 mAh g−1 retained over 1000 charge/discharge cycles at a high current density of 1 A g−1. This performance is much better than that MoS2/nitrogen-doped carbon nanoparticles (MoS2/CNP) composite. This work demonstrates the importance of introducing three-dimensional nanostructures in electrode materials to improve their electrochemical performance.