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Novel electrolyte additive for electrochemical capacitors has been reported. It has been demonstrated for the first time that addition of humic acids (HA) to KOH-based electrolyte significantly increases capacitance of symmetrical capacitors with electrodes made of activated carbon. Specific capacitances determined by means of galvanostatic charge/discharge, cyclic voltammetry and electrochemical impedance spectroscopy consistently showed increases for HA concentrations ranging from 2% w/w up to saturated solution with maximum positive effect observed for 5% w/w of the additive. The capacitance increase has been attributed to complex faradaic processes involving oxygen-containing groups of HA molecules. Due to abundant resources, low cost and easy processability the reported solution can find application in electrochemical capacitor technologies.
Sulfide-based all-solid-state batteries using a non-flammable inorganic solid electrolyte are promising candidates as a next-generation power source owing to their safety and excellent charge–discharge cycle characteristics. In this study, we thus focus on the positive electrode and investigated structural stabilities of the interface between the positive electrode active material LiNi1/3Mn1/3Co1/3O2 (NMC) and the 75Li2S·25P2S5 (LPS) glass electrolyte after charge–discharge cycles via transmission electron microscopy (TEM). To evaluate the thermal stability of the fabricated all-solid-state cell, in-situ TEM observations for the positive electrode during heating are conducted. As a result, structural and morphological changes are detected in the LPS glasses. Thus, exothermal reaction present in the NMC-LPS composite positive electrode after the initial charging is attributable to the crystallization of LPS glasses. On the basis of a comparison with crystallization behavior in single LPS glasses, the origin of exothermal reaction in the NMC-LPS composites is discussed.
LiNiO2, partially substituted with manganese in the form of a LiNi0.5Mn0.5O2 compound, has been synthesized by a gelatin assisted combustion method [GAC] method. Highly crystalline LiNi0.5Mn0.5O2 powders with R3m symmetry have been obtained at an optimum temperature of 850°C, as confirmed by PXRD studies. The presence of cathodic and anodic CV peaks exhibited by the LiNi0.5Mn0.5O2 cathode at 4.4 and 4.3V revealed the existence of Ni and Mn in their 2+ and 4+ oxidation states, respectively. The synthesized LiNi0.5Mn0.5O2 cathode has been subjected to systematic electrochemical performance evaluation, via capacity tapping at different cut-off voltage limits (3.0–4.2, 3.0–4.4 and 3.0–4.6V) and the possible extraction of deliverable capacity under different current drains (0.1C, 0.5C, 0.75C and 1C rates). The LiNi0.5Mn0.5O2 cathode exhibited a maximum discharge capacity of 174mAhg−1 at the 0.1C rate between 3.0 and 4.6V. However, a slightly decreased capacity of 138mAhg−1 has been obtained in the 3.0–4.4V range, when discharged at the 1C rate. On the other hand, extended cycling at the 0.1C rate encountered an acceptable capacity fade in the 3.0–4.4V range (<10%) for up to 50 cycles.
Control of action selection in the brain must be stable yet flexible. Using two-photon calcium imaging, the authors find distinct population activity states in secondary motor cortex for different stimulus–response contingencies and show that transitions between these states occurred earlier when mice were required to abort a repetitive action and use a conditional rule.
This work is a brief account of the most recent developments observed in the application of ZnO nanostructured materials in excitonic solar cells (organic, hybrid and dye sensitized solar cells). Special emphasis is made to one-dimensional (1D), vertically-aligned nanostructures (nanowires NW, nanorods NR) of ZnO semiconductor oxide and the extensive research work invested in recent years for its application as an electron acceptor material in solar cells. Our aim is to give the reader a broad overview of this semiconductor oxide and to understand the causes, advantages and disadvantages, for its application in a well-aligned nanostructure form. We briefly describe the most applied methodologies for its synthesis as well as the effect on surface area, electron transport and charge recombination when it is applied as an electron transport material in excitonic solar cells (XSCs). The importance of low-cost and easy-scalable synthesis techniques, as well as stability issues on these solar cells are discussed. Finally, we include a brief analysis of the possible future trends for the application of this interesting semiconductor oxide in XSCs.
The functionality and reliability of Li-ion batteries as major energy storage devices have received more and more attention from a wide spectrum of stakeholders, including federal/state policymakers, business leaders, technical researchers, environmental groups and the general public. Failures of Li-ion battery not only result in serious inconvenience and enormous replacement/repair costs, but also risk catastrophic consequences such as explosion due to overheating and short circuiting. In order to prevent severe failures from occurring, and to optimize Li-ion battery maintenance schedules, breakthroughs in prognostics and health monitoring of Li-ion batteries, with an emphasis on fault detection, correction and remaining-useful-life prediction, must be achieved. This paper reviews various aspects of recent research and developments in Li-ion battery prognostics and health monitoring, and summarizes the techniques, algorithms and models used for state-of-charge (SOC) estimation, current/voltage estimation, capacity estimation and remaining-useful-life (RUL) prediction.
A novel two-step approach was developed to fabricate well-dispersed Na1.08V3O8nanosheets, which consist of ultra-thin monolayer sheets with a thickness of ca. 10 nm. The formation mechanism of nanosheets involves the fusion and conversion of nanorods. When used as a cathode material for Li-ion batteries, the nanosheets show superior rate capability, with discharge capacities of ca. 200.0, 131.3, 109.9, 94.2 and 72.5 mA h g−1 at 0.4, 10, 20, 30 and 50 C, respectively. Excellent cycling stability without considerable capacity loss over 200 cycles is observed at 600 and 1000 mA g−1. It is believed that the unique nanosheet morphology as well as its intrinsic structural features greatly facilitate the kinetics of Li-ion diffusion and excellent structure stability, thus resulting in superior electrochemical performance.
Nanospherical-like manganese monoxide/reduced graphene oxide (MnO/rGO) nanocomposites are synthesized by using an electron beam radiation approach in an aqueous solution containing potassium permanganate and graphene oxide in the presence of acetone as radical scavenger and subsequently calcining in flowing Ar atmosphere. SEM and TEM observations show that nanospherical-like MnO with average size of 20nm are firmly anchored onto the rGO to form MnO/rGO nanocomposites. The typical MnO/rGO nanocomposite exhibits a high initial reversible capacity (977.1mAhg−1) at a current density of 150mAg−1 and delivers 648.4mAhg−1 at a rate of 750mAhg−1 with excellent cycling performance (89% of capacity retention over 50 cycles), which indicates that the MnO/rGO nanocomposite is a promising anode candidate for Li-ion batteries. Furthermore, the facile synthetic strategy by using an electron beam radiation provides a novel avenue for making high-performance metal oxide/graphene nanocomposites for energy storage applications.
Li2MnSiO4@C porous nanoboxes have been synthesized via a wet-chemistry associated solid-state reaction method. The uniqueness of this material is the hollow nanostructure with a well-crystalline porous shell composed of phase-pure Li2MnSiO4 nanocrystals, which has not been reported previously. As evidenced by powder X-ray diffraction patterns and transmission electron microscopy images, the high phase purity and porous nanobox architecture were achieved via monodispersed MnCO3@SiO2 core–shell nanocubes with controlled shell thickness. Nanocomposite of Li2MnSiO4@C and reduced graphene oxide nanosheets demonstrated excellent performance as high-capacity cathode materials for Li-ion batteries.
The aim of this study was to estimate average occupational exposure to inhalable nickel (Ni) using the German exposure database MEGA. This database contains 8052 personal measurements of Ni collected between 1990 and 2009 in adjunct with information on the measurement and workplace conditions. The median of all Ni concentrations was 9 μg/m3 and the 95th percentile was 460 μg/m3. We predicted geometric means (GMs) for welders and other occupations centered to 1999. Exposure to Ni in welders is strongly influenced by the welding process applied and the Ni content of the used welding materials. Welding with consumable electrodes of high Ni content (>30%) was associated with 10-fold higher concentrations compared with those with a low content (<5%). The highest exposure levels (GMs ≥20 μg/m3) were observed in gas metal and shielded metal arc welders using welding materials with high Ni content, in metal sprayers, grinders and forging-press operators, and in the manufacture of batteries and accumulators. The exposure profiles are useful for exposure assessment in epidemiologic studies as well as in industrial hygiene. Therefore, we recommend to collect additional exposure-specific information in addition to the job title in community-based studies when estimating the health risks of Ni exposure.
Nanostructured hybrids have attracted great interest in the development of high-performance supercapacitors. Herein, a novel hierarchical nanohybrid of La(OH)3 electrostatically anchored onto 2D-Graphene nanosheets (GNs) were prepared by a simple solvothermal reduction method and investigated as an electrode material for supercapacitors for the first time. This 2D La(OH)3-G nanohybrid electrode exhibits a specific capacitance of 485 F g−1 at 1 A g−1 and 295 F g−1 at 15 A g−1 with 61% of capacitance retention from 1 A g−1 to 15 A g−1 in 6 M KOH in the potential window of −0.2–0.4 V. This nanohybrid electrode provides a convenient and advantageous way for charge and ion transport and highly accessible electroactive sites to improve the performance of supercapacitors. The asymmetric supercapacitor assembled with La(OH)3-G nanohybrids as a positive electrode and activated carbon as negative electrode produce the highest specific capacitance of 69 F g−1 at of 1 A g−1 and retains 82.6% up to 5000 cycles with 97% Coulombic efficiency in 6 M KOH. These electrochemical findings demonstrate La(OH)3-G nanohybrid as a potential candidate for supercapacitor applications.
Electrochemical capacitor electrodes were fabricated by depositing an ultra-thin layer of vanadium oxide on a high conducting, large specific surface area (SSA) materials (substrates) using a supercritical fluid adsorption–calcination method. The high SSA materials included binder free single walled carbon nanotube–activated carbon (SWCNT–AC) composites and the traditional electrode of activated carbon–carbon black–polymer binder (AC–CB–binder). The uptake of the organometallic precursor for the oxide (vanadium (III) acetylacetonate) on the substrates were investigated and related to their SSA. Precursor uptakes up to 54.7 wt% of the initial carbon substrate was achieved. Calcination conditions for converting the precursor to oxide and electrochemical properties of the electrodes were thoroughly investigated. The V2O5, which showed extremely high specific pseudo-capacitance (>1000 F g−1 at 100 mV s−1), greatly enhanced the overall electrode performances. Conversely, the V2O5 pseudo-capacitance was better utilized in the SWCNT–AC substrate, particularly at high working speeds, because of the significantly higher electrical conductivity. For example, the SWCNT–AC–V2O5 composite (weight ratio 40:60) had its volumetric capacitance doubled, comparing to the ∼50% increase in the AC–CB–binder sample at 100 mV s−1.
The forthcoming ubiquitous innovations driven by flexible/wearable electronics and Internet of Things (IoT) have inspired the relentless pursuit of advanced power sources with versatile aesthetics. Here, we demonstrate a new class of solid-state flexible power sources that are fabricated directly on conventional A4 paper using a commercial desktop inkjet printer. A salient feature of the inkjet-printed power sources is their monolithic integration with paper, i.e., they look like inkjet-printed letters or figures that are commonly found in office documents. A supercapacitor (SC), which is composed of activated carbon/carbon nanotubes (CNTs) and an ionic liquid/ultraviolet-cured triacrylate polymer-based solid-state electrolyte, is chosen as a model power source to explore the feasibility of the proposed concept. Cellulose nanofibril-mediated nanoporous mats are inkjet-printed on top of paper as a primer layer to enable high-resolution images. In addition, CNT-assisted photonic interwelded Ag nanowires are introduced onto the electrodes to further improve the electrical conductivity of the electrodes. The inkjet-printed SCs can be easily connected in series or parallel, leading to user-customized control of cell voltage and capacitance. Notably, a variety of all-inkjet-printed SCs featuring computer-designed artistic patterns/letters are aesthetically unitized with other inkjet-printed images and smart glass cups, underscoring their potential applicability as unprecedented object-tailored power sources.
The FM01-LC is a laboratory-scale, electrochemical filter-press cell with a projected electrode area of 64cm2 and a rectangular electrolyte flow channel which was originally based on the larger FM21-SP electrolyser of 2100cm2 projected electrode area designed for the chlor-alkali industry then diversified to other applications. Many laboratories and industries have utilised this type of controlled flow reactor containing plane parallel electrodes in a rectangular channel for industrial and commercial applications. The diverse range of electrodes possible in such cells is emphasized with examples including 3-D metals and carbon, coated metal electrodes and nanostructured surfaces offering a high surface area. The experimental characterization and computational modelling of its reaction environment are concisely described discussed to appreciate the features of this type of electrochemical reactor. The cell construction and reaction environment are summarized, followed by an illustration of its use for a range of applications that include organic and inorganic electrosynthesis, metal ion removal, energy storage, environmental remediation (e.g., precious metal recycling or anodic destruction of organics) and drinking water treatment. Examples of the cell for energy conversion and storage (flow batteries and proton exchange membrane fuel cells) are briefly illustrated. The use of such a flow cell for the characterization of new electrochemical processes and to provide data enabling scale-up is considered.
Chrysanthemum-like carbon/FeS microspheres (CL-C/FeS) are prepared from a one-step solvothermal method. The morphology and structure of the CL-C/FeS are characterized by X-ray diffraction, scanning electron microscopy and high-resolution transmission electron microscope. We note that the prepared CL-C/FeS microspheres exhibit the average diameter of 15 μm and possess a sheet-on-sheet structure. FeS nanosheets are stacked on the carbon sheets to form a 2D sheet-on-sheet structure, these 2D C/FeS nanosheets are self-assembled to form a 3D chrysanthemum-like morphology. Due to the unique structure, CL-C/FeS microspheres show the excellent sodium-storage performance of 500 mAh g−1 at 0.2 A g−1 and 260 mAh g−1 at 1 A g−1, which are higher than those of most reported values. Therefore, the CL-C/FeS with appropriate structure is expected to be a competitive choice for anode materials for sodium ion batteries.
In this work, CoS nanoflakes were directly grown on graphene followed by sulfur storing by annealing sulfur/carbon disulfide and CoS nanoflakes at 155 °C for 10 h in N2. The microstructural and morphologies of the CoS/graphene nanoflake composites (CoS/G) were investigated by X-ray diffraction/photoelectron spectroscopy and electron microscopy. Benefiting from the strong chemical binds between CoS and lithium polysulfide species, and good electrical conductivity of graphene, the nanostructured sulfur cathode displays high sulfur utilization, promising rate capability and cycling stability compared to pristine sulfur cathode. The discharge capacity of the 100th cycle is maintained at 675.7 mA h g−1 at 0.5C.
Active somatosensory perception requires the integration of signals arising from both external stimuli and motor activity. The authors found a population of neurons in rat somatosensory cortex that responded to touch only when contact occurred at a specific phase in the whisk cycle, providing information about the position of the object relative to the rat's face.
The potential of reduced graphene oxide-molybdenum sulfide (rGO-MoS2) hybrid as a self-lubricating reinforcement in the Cu-based composites for enhancement of mechanical and tribological properties is presented. The rGO-MoS2 was synthesized by a hydrothermal approach using highly dispersed graphene oxide as a platform material to grow the MoS2 nanosheets. The Cu-rGO-MoS2 composites having 2 wt% of rGO-MoS2 were prepared at 600, 650, 700 and 750 °C to probe the effect of sintering temperature on mechanical and tribological properties. Microscopic images of Cu-rGO-MoS2 composites based on SEM and HRTEM measurements along with corresponding area elemental distribution suggested the nearly uniform dispersion of rGO-MoS2 hybrid in the copper matrix via multidimensional interactions. The composites exhibited significantly improved hardness compared to pure copper, and it was attributed to freezing of the movement of the dislocations by rGO-MoS2. Incorporation of rGO-MoS2 in Cu resulted in a remarkable reduction in both the coefficient of friction and the wear rate. The improved friction and wear performances of composites have been ascribed to the self-lubricating action of rGO-MoS2 hybrid and the formation of rGO-MoS2 containing tribo-film on the counter face steel ball which facilitated the sliding events and protected the tribo-pair against the wear.
Metal-air batteries are among the most promising next-generation energy storage devices. Relying on abundant materials and offering high energy densities, potential applications lie in the fields of electro-mobility, portable electronics, and stationary grid applications. Now, research on secondary zinc-air batteries is revived, which are commercialized as primary hearing aid batteries. One of the main obstacles for making zinc-air batteries rechargeable is their poor lifetime due to the degradation of alkaline electrolyte in contact with atmospheric carbon dioxide. In this article, we present a continuum theory of a commercial Varta PowerOne button cell. Our model contains dissolution of zinc and nucleation and growth of zinc oxide in the anode, thermodynamically consistent electrolyte transport in porous media, and multi-phase coexistance in the gas diffusion electrode. We perform electrochemical measurements and validate our model. Excellent agreement between theory and experiment is found and novel insights into the role of zinc oxide nucleation and growth and carbon dioxide dissolution for discharge and lifetime is presented. We demonstrate the implications of our work for the development of rechargeable zinc-air batteries.
In this work, cerium oxide nanoparticles are capable of strongly enhancing the chemiluminescence (CL) of the luminol–hydrogen peroxide (H2O2) system. Based on this, a microarray CL method for the determination of the removal rate constant of H2O2 by human erythrocytes has been developed. It is providing direct evidence for a H2O2-removing enzyme in human erythrocytes that acts as the predominant catalyst. A reaction mechanism is discussed. The proposed microarray CL method is sensitive, selective, simple and time-saving, and has good reproducibility and high throughput. Relative CL intensity is linearly related to the concentration of H2O2 in the range from 0.01 to 50 μM. The limit of detection is as low as 6.5 × 10−11 M (3σ), and the relative standard deviation is 2. 1 % at 1 μM levels of H2O2 (for n = 11).
The influence of CeO2 additions on the electrochemical behaviour of the MnO2 cathode in a Zn–MnO2 battery using lithium hydroxide (LiOH) as an electrolyte is investigated using microscopy and spectroscopic techniques. The results showed that such additions greatly improve the discharge capacity of the battery (from 155 to 190mAhg−1) but only from the second discharge cycle onwards. Capacity fade with subsequent cycling is also greatly reduced. With an aim to understand the role of CeO2 on the discharge–charge characteristics of MnO2 and its mechanism, we have used a range of microscopy, spectroscopy and diffraction-based techniques to study the process. The CeO2 is not modified by multiple discharged and charged cycles. The CeO2 may enhance the discharge–charge performance of the battery by raising the oxygen evolution potential during charging but does not take part directly in the redox reaction.
Numerous mnemonic techniques have been used and advocated throughout history. In this chapter, some of the most popular and enduring formal mnemonic and organizational mnemonic techniques are discussed in terms of their underlying processes. Specifically, the method of loci, the peg-word method, and the keyword method are discussed as formal mnemonic techniques. The use of acronyms, linking by story, and categorical and schematic organizations are discussed as organizational mnemonic techniques. As is described in the discussion, each of the mnemonic devices represents simple applications of well-researched psychological processes. Furthermore, examination of mnemonic techniques in light of basic research suggests that a specific combination of processes is necessary for the effectiveness of any given mnemonic.
The prefrontal cortex is specially adapted to generate persistent activity that outlasts stimuli and is resistant to distractors, presumed to be the basis of working memory. The pyramidal network that supports this activity is unknown. Multineuron patch-clamp recordings in the ferret medial prefrontal cortex showed a heterogeneity of synapses interconnecting distinct subnetworks of different pyramidal cells. One subnetwork was similar to the pyramidal network commonly found in primary sensory areas, consisting of accommodating pyramidal cells interconnected with depressing synapses. The other subnetwork contained complex pyramidal cells with dual apical dendrites displaying nonaccommodating discharge patterns; these cells were hyper-reciprocally connected with facilitating synapses displaying pronounced synaptic augmentation and post-tetanic potentiation. These cellular, synaptic and network properties could amplify recurrent interactions between pyramidal neurons and support persistent activity in the prefrontal cortex.
Na-ion batteries (NIBs) and Na-ion capacitors (NICs) have tremendous potential in many large-scale energy storage applications. Here, NIBs based on TiO2 nanorods/carbon fiber cloth (TiO2/CFC) flexible anode materials are introduced. The as-prepared flexible anode exhibited a notable rate performance and high specific capacity of 148.7 mAh g−1 after 2000 cycles at 1 A g−1. Furthermore, we demonstrate a highly flexible NIC system employing the TiO2/CFC anode and carbon fibers (CFs) as the cathode material. The flexible TiO2/CFC//CFs NIC device achieved a high energy density of 73.8 Wh kg−1 and high power density of 13,750 W kg−1, as well as long-term cycling stability over 4000 cycles with a capacity retention of ∼90%.