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Supercapacitors are electrochemical energy storage devices that operate on the simple mechanism of adsorption of ions from an electrolyte on a high-surface-area electrode. Over the past decade, the performance of supercapacitors has greatly improved, as electrode materials have been tuned at the nanoscale and electrolytes have gained an active role, enabling more efficient storage mechanisms. In porous carbon materials with subnanometre pores, the desolvation of the ions leads to surprisingly high capacitances. Oxide materials store charge by surface redox reactions, leading to the pseudocapacitive effect. Understanding the physical mechanisms underlying charge storage in these materials is important for further development of supercapacitors. Here we review recent progress, from both in situ experiments and advanced simulation techniques, in understanding the charge storage mechanism in carbon- and oxide-based supercapacitors. We also discuss the challenges that still need to be addressed for building better supercapacitors.
Organic–inorganic halide perovskite solar cells (PSCs) have achieved amazing progress in terms of power conversion efficiency (PCE), rising from 3.8% to over 23.3%. Owing to perovskites’ low nucleation and crystallization activation energy (56.6–97.3 kJ mol−1), a range of low temperature and large-scale solution fabrication processes have been actively investigated for potential commercialization. Although many excellent research institutes and enterprises have emerged to advance commercialization of PSCs, the performance of devices which have large areas still lag much farther behind those of smaller lab scales. The performances of PSCs are predominantly determined by the quality of the perovskite film, which in turn, is controlled by the fabrication process. A comprehensive and in-depth understanding of the nucleation and growth process during perovskite crystallization is imperative for the further advancement of large-scale manufacturing of high quality perovskite films. This review summarizes recent advances in the commercialization of the PSCs market, and critically reviews promising large-scale solution manufacturing methods combined with their physical properties and relevant challenges with the crystallization thermodynamics and kinetics of perovskites. The hurdles and challenges of commercialization and possible approaches and solutions are discussed.
The importance of early self-regulatory skill has seen increased focus in the applied research literature given the implications of these skills for early school success. A three-factor latent structure of self-regulation consisting of compliance, cool executive control, and hot executive control was tested against alternative models and retained as best fitting. Tests of model equivalence indicated that the model held invariant across Head Start and private child-care samples. Partial invariance was supported for age and gender. In the validity model, because of a substantial amount of shared variance among latent factors, we included a second-order factor explaining the two types of executive control. Higher order executive control positively predicted teacher report of learning behaviors and social competence in the classroom. These findings are discussed in light of their practical and theoretical significance.
Lithium-ion batteries have already achieved great success in consumer electronics. However, the electrochemical characteristics of the existing electrodes have constrained their widespread applications in electric vehicles, which need technical demands of high energy density and fast charging. Thus, it is highly desirable to explore high-performance electrodes with high reversible capacity and excellent rate capability. In this study, micro/nanostructured MnCo2O4.5 anodes were synthesized by hydrothermal treatment with the presence of positively charged poly(diallyldimethylammonium chloride). Physicochemical property studies suggested that the as-prepared MnCo2O4.5 of 2–5 µm in diameter was mainly composed of numerous nanoneedles, which were further comprised of many inter-connected nanoparticles. Also, poly(diallyldimethylammonium chloride) played the key roles as morphology controlling agent for the formation of the unusual MnCo2O4.5 crystal phase. The unique properties of micro/nanostructured MnCo2O4.5 including multi-scale dimensions, mesoporous structure, and multivalent states guaranteed the superior electrochemical characteristics in the repeated charge-discharge cycles. When evaluated as anodes for electrochemical lithium storage, high reversible capacity and good cycling performance were demonstrated with a current density of 500 mA g−1 over 200 cycles. Even when tested at relatively high current densities of 1000, 2000 and 3000 mA g−1, the average reversible capacities were also achieved at about 1441, 1213 and 966 mAh g−1, respectively. The achieved electrochemical characteristics of MnCo2O4.5 anodes were proved to be better than many binary transition metal oxides or comparable with high-capacity Si-based anodes. Overall, this study demonstrated micro/nanostructured MnCo2O4.5 as potential high-performance anodes for practical applications of next generation lithium-ion batteries.
In this paper, we report on one-pot synthesis of Ag nanoparticles/reduced graphene oxide (AgNPs/rGO) nanocomposites by heating mixed solution of graphene oxide (GO) and AgNO3 with the use of diethylenetriamine as a reducing agent at 80°C for 30min. Several analytical techniques including UV–vis spectroscopy, Raman spectroscopy and transmission electron microscopy (TEM) have been employed to characterize the resulting nanocomposites. It was found that such nanocomposites exhibit good catalytic activity toward the reduction of H2O2. This nonenzymatic H2O2 sensor shows a fast amperometric response time of less than 2s. The linear detection range is estimated to be from 0.1 to 100mM (r =0.999), and the detection limit is estimated to be 3.6μM at a signal-to-noise ratio of 3.
Results of the last 10 years of our investigations on the use of reticulated vitreous carbon (RVC®) in various types of cells show that this kind of porous conductive glassy carbon can be successfully used as a matrix for active mass and as a current collector in many primary and secondary batteries. This paper focuses mainly on the use of RVC® modified with metals like Pt, Rh, Pd, Ni, Pb and their oxides in construction of the following types of cells: (1) zinc-carbon primary and secondary batteries, (2) rechargeable cell systems with NiOOH cathode, (3) electrochemical capacitors with Pd and Pd–Rh alloys, and (4) lead acid battery. The most important improvement in performance has been achieved with lead-acid and zinc-carbon batteries. Especially for the modified zinc-carbon battery, which has been constructed in the popular AA format, manufactured on a small (laboratory) scale, and tested according to the IEC norms as a battery for commercial use, the capacity has been higher by ca. 20% compared with the batteries available on the market. Also, results obtained for thin layers of Pd and their alloys deposited on RVC® are promising in terms of the application of these kinds of electrodes in electrochemical capacitors. The pseudocapacitance of a Pd–Rh/RVC® composition may reach 540 F g−1.
Silicon is an attractive anode material for Li-ion cells, which can provide energy density 30% higher than any of the today's commercial Li-ion cells. In the current study, environmentally benign, high abundant, and low cost sand (SiO2) source has been used to prepare nano-silicon via scalable metallothermic reduction method using micro wave heating. In this research, we have developed and optimized a method to synthesis high purity nano silicon powder that takes only 5 min microwave heating of sand and magnesium mixture at 800 °C. Carbon coated nano-silicon electrode material is prepared by a unique method of coating, polymerization and finally in-situ carbonization of furfuryl alcohol on to the high purity nano-silicon. The electrochemical performance of a half cell using the carbon coated high purity Si is showed a stable capacity of 1500 mAh g−1 at 6 A g−1 for over 200 cycles. A full cell is fabricated using lithium cobalt oxide having thickness ≈56 μm as cathode and carbon coated silicon thin anode of thickness ≈9 μm. The fabricated full cell of compact size exhibits excellent volumetric capacity retention of 1649 mAh cm−3 at 0.5 C rate (C = 4200 mAh g−1) and extended cycle life (600 cycles). The full cell is demonstrated on an LED lantern and LED display board.
The environment surrounding Palmerton, Pennsylvania is contaminated with Pb arising from primary Zn smelting and a process involving Zn recovery from electric arc steel furnace dusts. Lead isotope systematics have been used to distinguish primary Zn smelting Pb (206Pb/204Pb∼18.4–18.5) from electric arc furnace dust lead (206Pb/204Pb∼19.0–19.1). Primary Zn smelting is the dominant source of Pb in O2 horizon soils from undisturbed near-Palmerton locations, which contain up to 3570 ppm Pb and 782 ppm Cd. Soils from undeveloped near-Palmerton locations also exhibit unusually elevated concentrations of other sphalerite-derived chalcophilic elements (Se, Ag, In, Sb, Te, Au, Hg, Tl and Bi); indium concentrations of up to 17.0 ppm are observed therein. Residential soils and dusts from Palmerton contain Pb which is largely explainable via mixing of Pb from primary Zn smelting and electric arc furnace dusts. Approximately 80% of the Pb in airborne particulate matter sampled at Palmerton in 1991 is derived from electric arc furnace dusts, and atmospheric enrichment factors for Cu, Sb, Pb, and Bi are observed which confirm this major source contribution. Residential samples from a control location contain Pb which is less radiogenic than is found in Palmerton, and exhibit no unusual elevation in sphalerite elements. Lead source discrimination in the Palmerton environment via Pb isotopic and elemental constituents approaches result in parallel conclusions.
World energy consumption is rising due to population growth and increasing industrialization. Traditional energy resources cannot meet these requirements with notice to their challenges, e.g., greenhouse gas emission and high lifecycle costs. Renewable energy resources are the appropriate alternatives for traditional resources to meet the increasing energy consumption, especially in electricity sector. Integration of renewable energy resources with traditional fossil-based resources besides storages creates Hybrid Renewable Energy Systems (HRESs). To access minimum investment and operation costs and also meet the technical and emission constraints, optimal size of HRES׳s equipment should be determined. One of the most powerful tools for this purpose is Hybrid Optimization Model for Electric Renewables (HOMER) software that was developed by National Renewable Energy Laboratory (NREL), United States. This software has widely been used by many researchers around the world. In this paper a review of the state-of-the-art of researches, which use HOMER for optimal planning of HRES, is presented.
It is demonstrated that β-Co(OH)2 has a high discharge capacity and good high-rate discharge ability as a negative electrode material. A new rechargeable battery system with higher energy density, consisting of α-phase nickel hydroxides as the positive electrode material and β-cobalt hydroxides as the negative electrode material, is proposed on the basis of multi-electron reactions.
The study presents technical, environmental and economic aspects for the selection of viable sites for constructing 10MW installed capacity grid connected photovoltaic power plants in Saudi Arabia. Available photovoltaic modules are analyzed and one is chosen for the analysis. Meteorological data like global solar radiation, sunshine duration, dry bulb temperature, and relative humidity was used to conduct the feasibility analysis using RETScreen software in terms of energy production, greenhouse gas (GHG) emissions, and financial parameters for the 44 sites. Bisha is found to be the best site for the installation of 10MW installed capacity grid connected photovoltaic power plant due to highest solar radiation intensity and longer sunshine duration. Both of these factors contribute to higher energy yield and less GHG emissions. On the lower extreme, Sulayel is found to be generating minimum energy from the same installed capacity of PV panels. Finally, it is recommended to commence constructing large grid-connected photovoltaic plant at Bisha with 70% government grant because the electricity export rate in Saudi Arabia is 72.57% cheaper than global price.
A low external temperature method (LETM) of active electrode material synthesis for lithium ion batteries has been proposed. The method consists of a two-step process, which is comprised of drying fine droplets of a solution of the starting compound in a liquid drying agent at 200 °C, followed by calcination of the obtained precursor in a fluidised bed at a furnace temperature of 300 °C. The method prevents uncontrolled growth of particles during the initial thermal pre-treatment and the final firing process. Lithium manganese spinel has been selected for describing the proposed LETM of synthesis. The properties of the spinel obtained by LETM are compared with those of a spinel obtained by the classical immobilised solid state synthesis at 750 °C. On electrochemical cycling, the capacity loss after 100 cycles of the LETM spinel at 11% is significantly lower than that for the spinel prepared by solid state methods (21.5%). However, only 3% difference is seen in the total integral capacity over the 100 cycles between spinels prepared by the different methods.
For the first time nanoporous germanium (np-Ge) was prepared by chemical dealloying allowing for mass production of electrodes for LiBs. Nanoporous structure can accommodate volume changes during the lithiation/de-lithiation progress and promote high-rate capability. The np-Ge shows a promising electrochemical performance as an advanced anode materials for LIBs with a specific capacity of 1191mAhg−1 after 160 cycles at a rate of 160mAg−1 and good rate capability.
It is still a great challenge to develop the long-life anode active materials for lithium ion batteries (LIBs) due to those issues resulting from the volumetric expansion of electrode materials during lithiation. Herein, we report the preparation of N-doped carbon (N-C) nanotubes encapsulated MnO nanoparticles with the size of 20–50nm by hydrolysis of metal coordination polymers (MCPs) in nitrogen gas, which is different from typical metal oxide/C core/shell nanostructures with conformal coating. The MnO/N-C nanotubes with an empty space between the nanoparticles allow for more volume expansion, which can effectively overcome existed issues such as MnO dissolution, disintegration, aggregation and volumetric expansion during the lithium ions insertion/extraction. When evaluated as electrode materials for lithium-ion batteries, the MnO/N-C nanotubes exhibit discharge and charge capacities of 1557.5 and 1171.0mAhg−1 in the initial cycle at 100mAg−1, respectively. And more impressively, the reversible capacity of 450.2mAhg−1 is remained after increasing the current density to 5Ag−1. Especially, the capacity steadily maintains at 804mAhg−1 even after 100 charge-discharge cycles at 1Ag−1.
ABSTRACT A new type of hierarchal mesoporous SnO2@C@TiO2 nanochains (SCT) as anode material for the lithium-ion batteries was prepared via a facile hydrothermal and kinetics-controlled coating method. The TiO2 shell and carbon shell act as double-decker protection to buffer the huge volume change of SnO2 during the charged and discharged process. The resulting batteries equipped with this novel anode material showed excellent cycling stability. SCT-250 with 8nm TiO2 external shell was demonstrated for optimal electrochemical performances. A high initial capacity of 807mAhg−1 was achieved at the current density of 100mAg−1 and maintained 369mAhg−1 after 100 cycles. The outstanding stable cycling and well rate performance suggest that SnO2@C@TiO2 core-shell-shell nanochains have great potential to be applied as anode material for lithium-ion batteries.
As a cathodic corrosion inhibitor and surfactant additive, the effects of calcium lignosulfonate (CLS) on the electrochemical behaviors of ZnO electrode were examined by polarization measurements, EIS (electrochemical impedance spectrum) and CV (cyclic voltammogram) electrochemical technique methods. Both of the corrosion current density and anodic Tafel slope for the ZnO with CLS additive (CZO) anode are smaller than those for the ordinary ZnO (OZO) anode, which indicates that the CLS has a good anticorrosion effect. Compared the CZO anode with the OZO anode, negative shift of the corrosion potential means CZO anode has a higher overpotential of hydrogen evolution. In order to explore the electrochemical corrosion performances of the zinc anodic process, further more studies such as morphological analysis, galvanostatic charge–discharge tests are also applied.
The core–shell type cathode material Li[(Ni0.8Co0.1Mn0.1)0.8(Ni0.5Mn0.5)0.2]O2 (CS) for Li-ion battery was synthesized via co-precipitation method. The electrochemical and thermal properties of the core–shell structured Li[(Ni0.8Co0.1Mn0.1)0.8(Ni0.5Mn0.5)0.2]O2 were compared with those of the average composition of core–shell Li[Ni0.74Co0.08Mn0.18]O2 (ACCS) and the mixture of the core Li[Ni0.8Co0.1Mn0.1]O2 and the shell Li[Ni0.5Mn0.5]O2 material (MCS). The CS shows the enhanced electrochemical properties in a high voltage range (4.5V and 4.6V) as well as the typical cut-off voltage range (4.3V). The capacity retentions of CS, core, and ACCS material were 94.2% (176.9mAhg−1), 86.6% (172mAhg−1), and 88.4% (169.3mAhg−1) after 120 cycles, respectively.
Summary In the case of electrodeposition from a formamide-water bath, application of pulse reverse waveforms improved the quality of deposits to very little extent, but these resulted in a bluish tinge. It seems that the quality of nickel electrodeposits is affected by the substrate, and both appearance and adhesion were much better for electrodeposits on copper or brass substrates.1.3 Nickel electrodeposition on low carbon steel substrates may require a special degreasing/cleaning process in order to improve adhesion and reduce internal stress.
The electrochemical and spectroelectrochemical properties of poly-(3,4-propylene-dioxythiophene-heptyl2) (PProDOT-heptyl2) film was studied by cyclic voltammetry, in situ UV–Visible spectroscopy, and in situ conductivity measurement. The cyclic voltammograms recorded for PProDOT-heptyl2 revealed redox peaks at 0.32/0.23V. The in situ conductivity of PProDOT-heptyl2 was measured at various potentials from −0.4V to +0.75V and found to be 0.19S/cm at +0.4V. Spectroelectrochemical experiments were performed to observe the absorption bands of the PProDOT-heptyl2 film in the neutral and oxidized forms. The derivative cyclic voltabsorptometric (DCVA) curves obtained for the PProDOT-heptyl2 film illustrated the presence of neutral, polaron, and bipolaron states. The absorption band of the polymer at 520nm is assigned due to the π–π∗ electronic transition of the film in the neutral state. The redox potentials of the polaron and bipolaron states were determined by DCVA to be +0.27V and +0.69V, respectively, which corresponds to the absorption bands of polaron at 760nm and of bipolaron at 710nm.
Nanostructured nickel oxide (NiO) thin films were prepared by a simple electrodeposition in choline chloride-based ionic liquid followed by an oxidation in air. Uniform granules and some voids opened between these granules were presented in the polycrystalline NiO films deposited for 10 and 30s, but the film became compact as the deposition time increased to 60s. The optical transmittance of the film decreased with the increase of the film thickness. All the NiO films exhibit high coloration efficiency, fast electrochromic switching and good cycling durability. The ultra fast switching time (0.74s and 0.88s) and maximum coloration efficiency of 250cm2 C−1 were observed for the film deposited for 10s.
Electrochemical behaviour of sandwich-type composite electrodes of polypyrrole (PPy) and CoFe2O4 nanoparticles (Ox) were investigated in an aqueous solution of 0.5M K2SO4 and 5mM KOH at 25 °C using electrochemical impedance (EI), cyclic voltammetry (CV) and Tafel polarization techniques. EI and CV studies indicated that the incorporation of oxide nanoparticles influenced the charge transfer and transport behaviours of the polymer matrix greatly. The bulk electrical resistances of pure polymer (4.5 ± 1.7Ω) as well as composite (2.7 ± 0.8Ω) electrodes were practically constant in the potential region, +0.1 to −0.7V. The latter electrode showed a good electrocatalytic activity towards the oxygen reduction reaction (ORR).
Three 26650 LiFePO4 (LFP) cells are cycled using a 40 A pulsed charge/discharge profile to study their performance in high rate pulsed applications. This profile is used to simulate naval pulsed power loads planned for deployment aboard future vessels. The LFP cells studied experienced an exponential drop in their usable high-rate recharge capacity within sixty cycles due to a rapid rise in their internal resistance. Differential capacitance shows that the voltage window for charge storage is pushed outside of the recommended voltage cutoff limits. Investigation into the state of health of the electrodes shows minimal loss of active material from the cathode to side reactions. Post-mortem examination of the anodic surface films reveals a large increase in the concentration of reduced salt compounds indicating that the pulsed profile creates highly favorable conditions for LiPF6 salt to break down into LiF. This film slows the ionic movement at the interface, affecting transfer kinetics, resulting in charge buildup in the bulk anode without successful energy storage. The results indicate that the use of these cells as a power supply for high pulsed power loads is hindered because of ionically resistant film development and not by an increasing rate of active material loss.
A new composite consisting of a mixture of zinc and hydrated ammonium zinc sulfate, Tutton salt, has been elaborated and studied as anode material for all-solid state protonic cells. The results obtained point out the ability of (NH4)2Zn(SO4)2·6H2O double salt to concomitantly exchange protons with the solid proton conducting electrolyte and accommodate Zn2+ cations issued from oxidation. Such features have been evinced by thermal and crystallographic characterizations. The anode composition has been optimized through a kinetic study on a three-electrode type-cell, showing that a 35wt.% salt-based composite displays the minimum polarization. Zn/MnO2 cells prepared using such a composite anode achieve relatively high specific capacity and energy of, more than 30Ahkg−1 and 40Whkg−1, respectively.