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The crystal chemistry and electrochemical performance of the layered LiNi0.5−y Co0.5−y Mn2y O2 and LiCo0.5−y Mn0.5−y Ni2y O2 oxide cathodes for 0≤2y ≤1 have been investigated. Li2MnO3 impurity phase is observed for Mn-rich compositions with 2y >0.6 in LiNi0.5−y Co0.5−y Mn2y O2 and 2y <0.2 in LiCo0.5−y Mn0.5−y Ni2y O2. Additionally, the Ni-rich compositions encounter a volatilization of lithium at the high synthesis temperature of 900°C. Compositions around 2y =0.33 are found to be optimum with respect to maximizing the capacity values and retention. The rate capabilities are found to bear a strong relationship to the cation disorder in the layered lattice. Moreover, the evolution of the X-ray diffraction patterns on chemically extracting lithium has revealed the presence of Li2MnO3 phase in addition to the layered phase for the composition LiNi0.25Co0.25Mn0.5O2 with an oxidation state of manganese close to 4+, which results in a large anodic peak at around 4.5V due to the extraction of both lithium and oxygen.
The American Conference of Governmental Industrial Hygienists (ACGIH) and some regulatory authorities have revised their exposure limits for nickel and nickel compounds in workplaces based upon new sampling standards for inhalable nickel exposures. Others may be in the process of doing so. Safe standards for workplace exposures should utilize the most up-to-date health data on individual nickel species and should incorporate the principles of new sampling conventions that have been developed over the recent decades. The purpose of this paper is to review the basis for setting inhalable occupational exposure standards for the principal inorganic nickel species. It is hoped that this paper will (1) prompt companies in various nickel industry sectors to begin collecting the necessary inhalable aerosol measurements, speciation data, and particle-size information required to implement health-based sampling programs in the future, and (2) encourage regulators to derive species-specific, inhalable-based workplace standards for nickel and its inorganic compounds.
To solve the continuing North Korean energy problem, the international community has provided, almost continuously, energy aid such as heavy fuel oil. Despite the large amount of energy aid North Korea has received, there is no evidence that the North Korean energy problem has gotten any better. Unless there is an structural energy reconstruction within North Korea, it portends the energy crisis there will only be exacerbated. Thus, North Korean energy solution cannot continue to remain at the level of providing direct aid, but should encompass a sustainable energy system that can answer the North's energy needs in mid- to long-term. Seeking a more permanent solution to solve the North Korean energy crisis, we contend renewable energy (RE) is a suitable option that can be used to build a sustainable energy system that North Korea can self-manage. From the South Korean energy policy perspective, that could be used to provide mid- and long-term energy solution for North Korea and fundamentally solve its energy crisis, this research sought to assess the South Korean residents’ preferences on burdening the cost associated with implementing a South Korean Government (SKG)-led RE support and cooperation policy for the North. We conducted a survey to assess the majority voting trends and approximately 30% of the respondents answered they had “no desire to pay.” The result showed that it would be difficult to fund an energy policy by making the South Korean populace directly shoulder the cost.
Supramolecular in-situ self-assembly is achieved to prepare carbon nanodots decorated graphene/polyaniline composites by adding β-cyclodextrin (β-CD) as the bonding agent in this work. With its unique structure, β-CD can form a supramolecular system with graphene oxide layers, generating the inclusion compound with aniline monomers, which makes the in-situ polymerization of polyaniline on the surface of graphene oxide. In the hydrothermal process, β-CD is carbonized to carbon nanodots anchored on the surface of reduced graphene oxide. The scanning electron microscopy (SEM) images show that the prepared reduced graphene oxide/carbon nanodots/polyaniline (RGO@CN/PANI) nanocomposites exhibit the micro morphology of a regular polyaniline particle array on the surface of graphene layers. The electrochemical tests demonstrate that the RGO@CN/PANI nanocomposites exhibit high specific capacitance (up to 871.8 F g−1 at 0.2A g−1), low charge transfer resistance (Rct), and presentable cycling performance (72% capacitance retention after 10000 cycles), indicating the satisfied performance for supercapacitors. The promising performance of RGO@CN/PANI can be attributed to the synergistic effect of RGO, carbon nanodots and PANI, as well as the regular microstructure in which the effective reaction area of polyaniline is increased and the rapid ion transport channel is provided.
Borazane (BH3NH3) is a stable and low-toxic crystalline solid with possibly the highest hydrogen content (19.5wt.%) in chemical compounds. In this communication, we report for the first time the electrooxidation of borazane and a novel direct fuel cell using alkaline borazane solution as alternative fuel. Of particular importance in this work is that non-platinum catalysts were applied for both the anode and the cathode. After a screening of a number of candidates (including Pt, Au, Ni, Cu, etc.), Ag was found to be a highly efficient catalyst for anodic oxidation of borazane, and MnO2 turned out to be a good cathode catalyst showing borazane-tolerance. The energy density of the fuel released by such a preliminary direct fuel cell was ca. 2000mAhg−1 at 1mAcm−2 and 0.9V at room temperature.
A novel gel polymer electrolyte (GPE) based on polyethylene glycol (PEG) composite lignocellulose (LC) with compact structure for application in lithium ion batteries (LIBs) is prepared. The GPE membrane dramatically enhances mechanical properties, and displays as high as 3–4 times than that of pure LC when adopting 30% PEG-1000. Meanwhile, the increased liquid electrolyte uptake is obtained (267%), and caused high ionic conductivity (3.22mScm−1) at room temperature. Moreover, the lithium ion transference number is as high as 0.81, much higher than most of reported separators, and shows good thermal and electrochemical stability. The rate and cycling performances further confirm that the GPE a very promising candidate for LIBs.
In this paper a recycling process for the recovery of zinc and manganese from spent alkaline and zinc–carbon batteries is proposed. Laboratory tests are performed to obtain a purified pregnant solution from which metallic zinc (purity 99.6%) can be recovered by electrolysis; manganese is recovered as a mixture of oxides by roasting of solid residue coming from the leaching stage. Nearly 99% of zinc and 20% of manganese are extracted after 3h, at 80°C with 10% w/v pulp density and 1.5M sulphuric acid concentration. The leach liquor is purified by a selective precipitation of iron, whereas metallic impurities, such as copper, nickel and cadmium are removed by cementation with zinc powder. The solid residue of leaching is roasted for 30min at 900°C, removing graphite completely and obtaining a mixture of Mn3O4 and Mn2O3 with 70% grade of Mn. After that a technical-economic assessment is carried out for a recycling plant with a feed capacity of 5000ty−1 of only alkaline and zinc–carbon batteries. This analysis shows the economic feasibility of that plant, supposing a battery price surcharge of 0.5€kg−1, with a return on investment of 34.5%, gross margin of 35.8% and around 3 years payback time.
A new class of difluoroalkoxyborane compounds ([R n OBF2]2) containing oligooxyethylene groups of various molecular weight in the form of a methyl monoether (R n =CH3(OCH2CH2) n , n =1, 2, 3 and 7) has been obtained in the reaction of BF3 etherate with appropriate glycols. 1H, 11B and 19F NMR spectral analysis of the derivatives obtained was carried out and the properties as Lewis acids of these derivatives have been compared with that of corresponding trialkoxyboranes and boron trifluoride in reaction with pyridine. The strength of the interaction of [R2OBF2]2 with the differing in “hardness” anions of various lithium salts has been analyzed on the basis of NMR spectra. The [R n OBF2]2 obtained were used as additives for polymer electrolytes containing PEO as polymer matrix and various lithium salts at an equimolar ratio of the boron compound to salt. The highest ionic conductivities, in the order 10−5 to 10−4 Scm−1 at 20–70°C, were achieved for systems containing LiI and LiN(CF3SO2)2. The lithium transference number (t +) values, determined by the electrochemical method by steady-state technique for LiF and LiCF3SO3 are in the 0.6–0.8 range.
The Mali Multifunctional Platform (MFP)—a government managed, multilaterally sponsored energy program that distributed a small diesel engine attached to a variety of end-use equipment—expanded access to modern energy services and raised village incomes from 1999 to 2004. Over this period, it successfully distributed more than 500 MFPs throughout Mali, and in doing so empowered women, improved educational opportunities, and enhanced food security and community cohesion. The MFP has also motivated the government to install 1800 such platforms by the end of 2012. Based on original research interviews supplemented with an extensive literature review, this study introduces readers to the rural energy situation in Mali and describes the history of the MFP project. It then discusses the benefits the project achieved, as well as five sets of challenges the MFP faces: a growing number of non-functional platforms, lack of policy coordination, poverty, dependence on imported technology and fuel, and patriarchy. The study concludes by offering six lessons for energy development planners and practitioners.
To improve the thermal shrinkage of the separators that are essential to securing the electrical isolation between electrodes in lithium-ion batteries, we develop a new separator based on a ceramic composite membrane. Introduction of microporous, ceramic coating layers onto both sides of a polyethylene (PE) separator allows such a progress. The ceramic coating layers consist of nano-sized alumina (Al2O3) powders and polymeric binders (PVdF-HFP). The microporous structure of the ceramic coating layers is observed to be crucial to governing the thermal shrinkage as well as the ionic transport of the ceramic composite separators. This microporous structure is determined by controlling the phase inversion, more specifically, nonsolvent (water) contents in the coating solutions. To provide a theoretical basis for this approach, a pre-investigation on the phase diagram for a ternary mixture comprising PVdF-HFP, acetone, and water is conducted. On the basis of this observation, the effect of phase inversion on the morphology and air permeability (i.e. Gurley value) of ceramic coating layers is systematically discussed. In addition, to explore the application of ceramic composite separators to lithium-ion batteries, the influence of the structural change in the coating layers on the thermal shrinkage and electrochemical performance of the separators is quantitatively identified.
In this study, the authors show that they can induce the direct conversion of fibroblasts into nociceptor neurons via the expression of only five key transcription factors. They further confirm that these induced neurons are bona fide nociceptors by demonstrating that their expression profiles resemble that of their endogenous counterparts and show that they are responsive to common nociceptor agonists.
Vanadium redox flow battery (VRFB) is attractive for energy storage applications, but there still remains a problem of preventing V-precipitation reaction (i.e., V2O5) to provide the thermal stability of electrolyte employed in VRFB. The V2O5 precipitation is accelerated in the positive electrolyte under high temperature, resulting in decreasing the charge capacity and energy efficiency of VRFB. So far, previous supporting materials, which are used to solve such precipitation problem, provide a disadvantage of decreasing voltage efficiency of VRFBs by increasing electrolyte resistance. This paper describes an advanced vanadium-positive electrolyte with high-temperature tolerance for high-efficiency VRFBs, which uses a sodium formate as a supporting material. The sodium formate plays a role as an agent capable of preventing precipitation reaction in the positive electrolyte and it also provides an effect of decreasing a viscosity of the positive electrolyte. The effectiveness of the proposed electrolyte solution is demonstrated through the following experiments: UV–vis spectrometry, viscosity measurement, cyclic voltammetry (CV), VRFB operation and scanning electron microscopy (SEM) analysis. Then, for the performance comparison of high temperature stability, all experiments are carried out at 60°C. Experimental results show that using the sodium formate leads to near 4.5 times increase of diffusion coefficient as compared to conventional electrolyte, and also provides 20.2% higher charge capacity (50th cycle) and 2.27% higher average energy efficiency (50cycles) at the current density of 80mAcm−2. In addition, it appears that the precipitation of vanadium species is not observed in the electrolyte during VRFB operation. Therefore, this paper provides that new direction about effect of the additive in the positive electrolyte and the sodium formate can be considered as a promising additive for high-performance electrolyte of VRFBs.
Designing and preparing flexible supercapacitor electrode with high specific capacitance and good cycle stability is still a severe challenge. In this study, a sandwich-like nickel oxide/nanoporous nickel/metallic glass (NiO/np-Ni/MG) composite electrode was facilely synthesized by dealloying the Ni45Ti20Zr25Al10 MG ribbons in O2-rich HF solution. Different from the routine free-dealloying, the etching with continuous O2 flow in HF results in the in-situ growth of NiO micro-rod arrays on np-Ni surface. The shape of NiO from an initial flower-like architecture evolves to be the regular hexagonal pillars during the O2-assisted dealloying process. The possible nucleation and growth mechanism of hexagonal NiO is proposed. Moreover, the as-designed sandwich-like structure offers an excellent flexibility of the composite electrode due to the high ductile Ni-based MG interlayer. Meanwhile, the new-type NiO/np-Ni/MG electrodes demonstrate a high specific capacitance (745.3 F/cm3 at 0.5 A/cm3) in KOH solution and excellent cycling stability (92% retention after 6000 cycles at 20 mV/s). The symmetric supercapacitor (SC) devices were successfully assembled by using the dealloyed ribbons and showed a maximum volumetric energy density of about 19.82 mW h/cm3 at a power density of 0.4 W/cm3, and even kept at 8.71 mW h/cm3 when the power density increased to 1.6 W/cm3. The fully charged two SC devices connected in series could light up a red LED bulb for more than 10 min. The novel developed NiO/np-Ni/MG electrodes with good energy storage performance and excellent flexibility show highly promising application potential in wearable energy storage devices.
The introduction of microgrids in distribution networks based on power electronics facilitates the use of renewable energy resources, distributed generation (DG) and storage systems while improving the quality of electric power and reducing losses thus increasing the performance and reliability of the electrical system. The hierarchical control structure, which consists of primary, secondary, and tertiary levels for microgrids that mimic the behavior of the mains grid, is reviewed. The main objective of this article is to give a description of state of the art for distributed power generation systems (DPGS) based on renewable energy and explore the power converters connected in parallel to the grid which are distinguished by their contribution to the formation of the grid voltage and frequency and are accordingly classified in three classes. This analysis is extended focusing mainly on the three classes of configurations: grid-forming, grid-feeding, and grid-supporting. The article ends up with an overview and a discussion of the control structures and strategies to control distribution power generation system (DPGS) units connected to the network.
In-situ Raman spectroscopy is employed to investigate the valence state variations of nickel and manganese, as well as the local structure change of LiMn1.45Ni0.45 M 0.1O4 (M = Cr, Co) cathodes (LMN) during galvanostatic charge–discharge. Raman spectra are collected between 3.5 and 4.9 V in the wave number range of 100–800 cm−1. The Raman observations showed that the pristine cathodes of Cr- and Co-doped LMN have essentially the same spectra, and they also have similar evolution patterns during cycling showing their reversible behaviour in the de-lithiation and lithiation processes. The Raman spectra of the pristine cathodes have eleven bands, located at 162, 220, 378, 408, 486, 498, 528, 593, 613, 639 and 672 cm−1. The bands with wave number <300 cm−1 are attributed to the translation mode of molecular vibration; the 486, 593 and 639 cm−1 bands are assigned to the stretching mode of Mn–O bond; and the vibration modes at 408, 498, 528 and 613 cm−1 originated from the Ni–O bond; The band at 672 cm−1 is attributed to A 1g mode of Cr3+–O/Co3+–O. During cycling, several new bands are detected near the end of charge, among which the T 2g (T) band at 170 cm−1 is attributed to the translation mode of lattice vibration in which the lithium concentration is low, and the T 2g band at 538 cm−1 is due to the presence of Ni4+–O bond in the crystal structure. The T 2g(T) and T 2g(Ni4+–O) bands are clearly evident at V ≥ 4.78 (x ∼ 0.32) and V ≥ 4.82 (x ∼ 0.28) for Cr- and Co-doped LMN, respectively.
A facile synthesis of a metal oxide (ZrO2) coating on the surface of high voltage type Li2CoPO4F cathode material using the conventional solution method is reported in this study. The Li2CoPO4F is prepared by a two step solid state method, followed by the application of wet coating containing various amounts of ZrO2. Among the samples, the 5 wt% ZrO2 coated Li2CoPO4F material shows the best performance with an initial discharge capacity of up to 144 mA h g−1 within the voltage range of 2–5.2 V vs Li at 10 mA g−1. Moreover, this ZrO2 coated cell demonstrates an enhanced capacity retention which is two times higher than that of the uncoated sample. The reversible extraction–insertion of one lithium unit from Li2CoPO4F is successfully carried out in a controlled environment, where the electrolyte decomposition is reduced using a highly durable ZrO2 coating. The nanosized coating over the Li2CoPO4F surface helps to attain a higher discharge capacity even at high current rates. As a consequence, the cell delivers a capacity of 104 mA h g−1 at a high current rate of 100 mA g−1.
Electrochemical impedance analysis, in-situ dilatometry, in-situ electrochemical calorimetry and ex-situ SEM have been shown to be effective diagnostics for studying formation of dendrites in cells. Effect of lithium polysulfides present in the electrolyte in a Li–S cell, on the suppression of fine-dispersed heterogenous non-planar lithium dendrite precipitations during cycling of lithium symmetric cells was studied in accelerated DC cycling tests by a combination of the above techniques. It is shown that deliberate incorporation of lithium polysulfides in electrolyte solutions leads to decreasing rate of accumulation of fine-dispersed lithium (dendrite precipitations) on the surface of a lithium electrode which results in increasing the cycle life of lithium symmetric cells by 200–250% in accelerated tests, thus enhancing safety. It is demonstrated that electrochemical dilatometry and EC calorimetry are sensitive to changes on the surface of lithium electrode and can be used for early identification of dendrite formation during cycling of lithium electrodes. In-situ electrochemical dilatometry can not only identify formation of Li dendrites at early stages but also quantify the growth rate. The presence of high surface area lithium is more corrosive towards the electrolyte and can be monitored by the use of in-situ EC calorimetry for heat generation by corrosion during a cycle. Cycle life is limited by evenness/continuity of electrolyte solution in cell, which must essentially fill internal volume of the cell (all the pores without leaving any “dry area”).
The battery energy-storage industry is evolving rapidly so new battery components are needed with high stability and improved energy density, as well as enhanced safety. In this paper, results on new salts, safer degradation and good electrochemical performances are reported. Four organic anions for Li-salts were synthesized and their conductivity, viscosity and electrochemical potential window in EC/DEC (3/7) solutions were examined. These salts have high thermal stability and safer degradation products (compared to LiPF6 and Li-TFSI), which were identified by TGA-MS. Cyclic voltammetry measurements showed their electrochemical window and oxidation limits were at least 4.3 and 4.5 V vs Li/Li+ using a platinum and high surface area carbon material working electrode, respectively. The salts passivated the common aluminum current collector at 4.4 V vs Li/Li+ and without corrosion. The properties of one Li salts were evaluated in half cell configuration as a model system using lithium iron phosphate (LFP), lithium titanate oxide (LTO) and graphite as electrodes. The performance of the salt showed promising behavior in the model system, compared to benchmark salts such as LiPF6 and Li-TFSI.
The energy storage of activated carbon modified with a semiconducting oxide TiO2 is studied. The composite was prepared by mixing nanosize TiO2 and activated carbon through a means of ultrasonic vibration in ethanol solution for 30min. It was found that with modification of TiO2, the specific capacitance of activated carbon measured at 0.65mA/cm2 was increased from 47.2 to 63.1Fg−1. This method is unique in comparison the conventional method because it uses semiconducting TiO2 other than electrochemically active materials such as RuO2. The later has been adopted to make electrochemical-double-layer hybrid supercapacitors, however, the former is attributed to a pure double-layer supercapacitor.
The stability of underpotentially deposited (UPD) Pb layer on Cu(111) is investigated by conventional electrochemical techniques in perchlorate solution at open circuit potential (OCP). In situ scanning tunneling microscopy (STM) is employed to monitor and ascertain structural and morphological changes at characteristic potentials. A corrosion-like mechanism associated with UPD layer stripping powered by reduction processes is found to operate in the system of interest in absence of potential control. OCP transients suggest strong dependence of the Pb layer stability upon the concentration of oxidizing agents, such as oxygen and/or nitrate ions, present in the solution. It is found that the increase of the oxidizing agent concentration results in a proportional decrease of the Pb UPD layer stripping time at OCP. The concentration of the dissolved oxygen is found to affect the UPD layer behavior in the entire range of underpotentials in accordance with the strong affinity of the Pb2+/Cu(111) system to the oxygen reduction reaction (ORR). In contrast to oxygen, nitrate ions appear to play active role only in the potential range positive to the UPD peaks where mostly bare Cu surface is in contact with the solution. Specifically adsorbing Cl− ions are examined as a possible inhibitor of the reduction processes operating in the Pb underpotential range. Concentrations of Cl− ions as low as 1×10−4 M are found to stabilize the Pb UPD layer by a factor of 2.5.