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Lithiated perfluorosulfonate ionomer has been used as the binder for LiMn2O4 cathodes. Casted membranes of the lithiated ionomer exhibit ionic conductivity of 1.4×10−4 S/cm. Composite cathodes composed of LiMn2O4, carbon black and the ionomer binder have been fabricated. All components of the cathodes are well bound and dispersed as characterized by scanning electron microscope and energy dispersive spectroscope. The cathodes using the conventional poly-vinylidene fluoride binder have also been prepared for comparison. Under high rate (5 C-20C) and high temperature (60°C) operation, the LiMn2O4 cathodes with the ionomer binder exhibit higher capacity and improved cycling stability. As indicated by the electrochemical impedance spectra, the ionomer binder forms ion-conducting interface layers on the LiMn2O4 particles and results in lower interface resistance. It enables the cells utilizing the ionomer binder to achieve higher capacity and enhanced cycling stability even under harsh conditions.
A novel Pb x O y @SiO z /Carbon (PSC) composite has been synthesized and added with quantities between 0 wt% and 2 wt% to the negative active material of lead-acid batteries in this paper. Unique morphology of the obtained composite is detected by scanning electron microscopy (SEM) and transmission electron microscope (TEM), while the Pb x O y is coated by SiO2 firstly and then the obtained spherical particles are wrapped by amorphous carbon as a whole. The electrochemical characterizations are performed using a three-electrode system, and results show that the hydrogen evolution reaction (HER) can be inhibited compared with sole carbon. Finally, 2.0 V single-cell lead-acid batteries are assembled with 0 wt%–2 wt% PSC additive in the negative active materials (NAM). Battery with 0.5 wt% PSC exhibit the most superior performance including the highest capacity as well as the best high-rate partial state-of-charge (HRPSoC) cycling performance due to the integrative actions, which are investigated in detail in this paper.
With the advancement of the smart grid, the current energy system is moving towards a future where people can buy what they need, can sell when they have excess and can trade the right of buying to other proactive consumers (prosumers). Although the first two schemes already exist in the market, selling the right of buying — also known as negawatt trading — is something that is yet to be implemented. Here we review the challenges and prospects of negawatt trading in light of recent technological advancements. Through reviewing a number of emerging technologies, we show that the necessary methodologies that are needed to establish negawatt trading as a feasible energy management scheme in the smart grid are already available. Grid interactive buildings and distributed ledger technologies, for instance, can ensure active participation and fair pricing. However, some additional challenges need to be addressed for fully functional negawatt trading mechanisms in today’s energy market.
In this work, we prepare a highly catalytic and stabilized titanium nitride (TiN) nanowire array-decorated graphite felt electrode for all vanadium redox flow batteries (VRFBs). Free-standing TiN nanowires are synthesized by a two-step process, in which TiO2 nanowires are first grown onto the surface of graphite felt via a seed-assisted hydrothermal method and then converted to TiN through nitridation reaction. When applied to VRFBs, the prepared electrode enables the electrolyte utilization and energy efficiency to be 73.9% and 77.4% at a high current density of 300 mA cm−2, which are correspondingly 43.3% and 15.4% higher than that of battery assembled with a pristine electrode. More impressively, the present battery exhibits good stability and high capacity retention during the cycle test. The superior performance is ascribed to the significant improvement in the electrochemical kinetics and enlarged active sites toward V3+/V2+ redox reaction.
Neuroprosthetic technologies for therapeutic neuromodulation have seen major advances in recent years but these advances have been impeded due to electrode failure or a temporal deterioration in the device recording or electrical stimulation potential. This deterioration is attributed to an intrinsic host tissue response, namely glial scarring or gliosis, which prevents the injured neurons from sprouting, drives neurite processes away from the neuroelectrode and increases signal impedance by increasing the distance between the electrode and its target neurons. To address this problem, there is a clinical need to reduce tissue encapsulation of the electrodes in situ and improve long-term neuroelectrode function. Nanotopographical modification has emerged as a potent methodology for the disruption of protein adsorption and cellular adhesion in vitro. This study investigates the use of block copolymer self-assembly technique for the generation of sub-20 nm nanowire features on silicon substrates. Critically, these nanostructures were observed to significantly reduce electrical impedance and increase conductivity. Human neuroblastoma SH-SY5Y cells cultured on nanowire substrates for up to 14 days were associated with enhanced focal adhesion reinforcement and a reduction in proliferation. We conclude that nanowire surface modulation may offer significant potential as an electrode functionalization strategy.
A Li2FeSiO4/C nanocomposite is prepared via solvothermal method in combination with carbon coating technology. The as-prepared Li2FeSiO4/C nanocomposite is a single phase Li2FeSiO4 with nano-tickness coated carbon layer and connected by the mutual cross-linked carbon conductive matrix. As cathode material for lithium ion battery, the composite delivers a discharge capacity of 154 mAh g−1 at 1C and exhibits good rate capability with a discharge capacity of 106 mAh g−1 at the rate of 10C, which is ascribed to the small particle size and enhanced electronic conductivity using carbon coating technology. The as-prepared Li2FeSiO4/C nanocomposite also behaves a good cycling stability with capacity retention of over 100 cycles.
Li2FeSiO4/C cathodes were synthesized by combination of wet-process method and solid-state reaction at high temperature, and effects of roasting temperature and modification on properties of the Li2FeSiO4/C cathode were investigated. The XRD patterns of the Li2FeSiO4/C samples indicate that all the samples are of good crystallinity, and a little Fe3O4 impurity was observed in them. The primary particle size rises as the roasting temperature increases from 600 to 750°C. The Li2FeSiO4/C sample synthesized at 650°C has good electrochemical performances with an initial discharge capacity of 144.9mAhg−1 and the discharge capacity remains 136.5mAhg−1 after 10 cycles. The performance of Li2FeSiO4/C cathode is further improved by modification of Ni substitution. The Li2Fe0.9Ni0.1SiO4/C composite cathode has an initial discharge capacity of 160.1mAhg−1, and the discharge capacity remains 153.9mAhg−1 after 10 cycles. The diffusion coefficient of lithium in Li2FeSiO4/C is 1.38×10−12 cm2 s−1 while that in Li2Fe0.9Ni0.1SiO4/C reaches 3.34×10−12 cm2 s−1.
It has recently been demonstrated that the use of anion exchange membranes (AEMs) in vanadium redox flow batteries (VRFBs) can reduce the migration of vanadium ions through the membrane due to the Donnan exclusion effect among the positively charged functional groups and vanadium ions. However, AEMs are plagued by low chemical stability in harsh chemical environments. Here we propose and fabricate a pyridinium-functionalized cross-linked AEM for VRFBs. The pyridinium-functionalized bromomethylated poly (2,6-dimethyl-1,4-phenylene oxide) exhibits a superior chemical stability as a result of the strengthened internal cross-linking networks and the chemical inertness of the polymer backbone. Therefore, the membrane exhibits littler decay in a harsh environment for 20 days during the course of an ex situ immersion test. A cycling test also demonstrates that the VRFB assembled with the membrane enable to retain 80% of the initial discharge capacity over 537 cycles with a capacity decay rate of 0.037% cycle−1. Meanwhile, the membrane also shows a low vanadium permeability and a reasonably high conductivity in supporting electrolytes. Hence, all the measurements and performance tests reported in this work suggest that the membrane is a promising AEM for redox flow batteries to achieve excellent cycling stability and superior cell performance.
In many low- and middle-income countries, insufficient human resources limit access to oral health services. Shifting clinical tasks to less specialized health professionals, such as community health workers, has been used as a strategy to expand the health workforce, especially in remote or underserved locations. The objective of this study was to evaluate the validity of periodontal examinations conducted by auxiliary nurse midwives in a rural home setting in Nepal.
Full-scale speed trials of a ship have been questioned for the uncertainty of speed and power measurements especially when the sea conditions differ from the ideal calm water conditions. Such uncertainty has been investigated by utilizing ITTC standard speed/powering trial analysis procedure through Monte Carlo simulations. A case study was conducted for a set of sea trials with 12 sister ships for which sea trial data were available for a range of displacement, water depth, water temperature, wind speed and wave height values. Precision errors were observed as the most influential error source for the whole speed range, even though their effects were more substantial at low speeds. Beaufort scale was observed as the most important elementary error source indicating the need for the best weather conditions for the most reliable sea trail predictions.
Hierarchical CoO nanosheets are grown on copper foils, by combining electro-deposition and self-sustained hydrothermal treatments and directly used as binder free anode electrodes of LIBs. CoO nanosheets are ∼50nm in thickness with several micrometers in width. The CoO nanosheets deposited on the copper foils were found to be single phase. The electrode delivers a capacity of ∼637mAhg−1 after 200 cycles at 0.1C and exhibits excellent rate capability, owing to the special hierarchical structure, preferable accommodation of strain, good conductivity and fast lithium ion diffusion. The capacity can be improved to ∼704mAhg−1 after carbon coating. The improved performance is investigated in detail. The results suggest that ameliorative conductivity, pseudocapacitance and the higher-oxidation-state component are responsible for the high capacity. More significantly, the strategy of CoO nanosheets fabrication not only can be extended to other substrates, such as carbon foams, carbon paper and carbon cloth, but can be applied to other materials, such as Fe3O4, NiO, etc.
Increasingly, Extended Producer Responsibility (EPR) and Product Stewardship (PS) frameworks are being adopted as a preferred policy approach to promote cost-effective diversion and recovery of post-consumer solid waste. Because the application of EPR/PS generally requires the creation of a separate and often parallel collection and/or management system, key to increasing the amount of waste recovered is to maximize the convenience of the collection system to maximize consumer participation. Convenient collection is often mandated in EPR/PS laws, however it is not defined. Convenience is a subjective construct rendering it extremely difficult to define. However, based on a dissection of post-consumer collection efforts under a generic EPR/PS system, this paper identifies and examines five categories of convenience – knowledge requirements, proximity to a collection site, opportunity to drop-off materials, the draw of the collection site, and the ease of the process—and the various factors of convenience within each of these categories. By using a simplified multiple criteria decision analysis, this paper proposes a performance matrix of criteria of convenience. Stakeholders can use this matrix to assist in the design, assessment, and/or implementation of a convenient post-consumer collection system under an EPR/PS framework.
The ageing of lithium-ion battery (LIB) is critical from the application perspective. In this paper, an electrochemical based electrical (ECBE) model is developed to link the model parameters to specific ageing mechanisms. Based on the model parameterization, we report on time resolved degradation processes of LIB during the cycle ageing. The sequence of internal components degradation mechanisms in graphite/lithium cobalt oxide (LCO) coin cells subjected to up to 1000 galvanostatic charge-discharge cycles are revealed. It is found the LIB degradation proceeds according to a series of inter-connected processes, including: i) Solid electrolyte interphase (SEI) formation on the graphite electrode surfaces; ii) LCO phase transformation from active hexagonal to less active spinel phases; iii) Joule heating due to the increased cell resistance resulting in cracking and re-formation of SEI together with surface spallation at the LCO electrode, as well as degradation of the separator; iv) Active Li losses owing to metal plating on the electrodes during overcharge and overdischarge; v) Exfoliation of the graphite anode and the degradation of LCO cathode; and vi) Intergranular contact disconnection within electrodes. These processes contribute to the overall decay in the storage capacity and the LIB terminal voltage differently as shown experimentally.
Attempts to dope Zn2+, Cu2+ or Ni2+ are made for Li2FeSiO4. The effects of dopant on the physical and electrochemical characteristics of Li2FeSiO4 were investigated. Zn2+ successfully entered into the lattice of Li2FeSiO4 and induced the change of lattice parameters. Compared with the undoped Li2FeSiO4, Li2Fe0.97Zn0.03SiO4 has higher discharge capacity, better electrochemical reversibility and lower electrode polarization. The improved electrochemical performance of Li2Fe0.97Zn0.03SiO4 can be attributed to the improved structural stability and the enhanced lithium ion diffusivity brought about by Zn2+ doping. However, Ni2+ and Cu2+ cannot be doped into the lattice of Li2FeSiO4. Cu and NiO are formed as impurities in the Cu- and Ni-containing samples, respectively. Compared with the undoped Li2FeSiO4, the Cu- and Ni-containing samples have lower capacities and higher electrochemical polarization.
While the market for supercapacitors is rapidly growing due to their high power density, their low energy density compared to batteries represents a great barrier for the future of this technology. The poorly understood chemistry of electrode-electrolyte interfaces implies that there is substantial room for improvement through a careful design of the materials involved. Here we present a unique approach for improving the energy density of supercapacitors through redox additive-assisted electrocatalytic in situ regeneration of the electrode active materials. By utilizing a quinone-based redox electrolyte and a nanostructured conjugated polyaniline electrode, we continually regenerate the reactants, resulting in a redox supercapacitor having an extremely high energy density of 1091Whkg−1 (based on the total mass of the electrode active materials and the redox additive) and a high power density up to 196kWkg−1. Considering the other outstanding properties of the polyaniline-naphthoquinone system, such as extreme flexibility (96% capacity retention after bending at an angle of 180° for 1000 cycles), non-flammability, and excellent cycling stability (84% capacity retention after 7000 cycles at 35Ag−1), such a well designed in situ regeneration of the electrode active materials makes this method a very promising approach towards the development of state-of-the-art energy storage devices.
Understanding (electro-)chemical reactions at the electrode–electrolyte interface (EEI) is crucial to promote the cycle life of lithium-ion batteries. In this study, we developed an in situ Fourier-transform infrared spectroscopy (FT-IR) method, which provided unprecedented information on the oxidation of carbonate solvents via dehydrogenation on LiNixMnyCo1−x−yO2 (NMC). While ethylene carbonate (EC) was stable against oxidation on Pt up to 4.8 VLi, unique evidence for dehydrogenation of EC on LiNi0.8Co0.1Mn0.1O2 (NMC811) at voltages as low as 3.8 VLi was revealed by in situ FT-IR measurements, which was supported by density functional theory (DFT) results. Unique dehydrogenated species from EC were observed on NMC811 surface, including dehydrogenated EC anchored on oxides, vinylene carbonate (VC) and dehydrogenated oligomers which could diffuse away from the surface. Similar dehydrogenation on NMC811 was noted for EMC-based and LP57 (1 M LiPF6 in 3:7 EC/EMC) electrolytes. In contrast, no dehydrogenation was found for NMC111 or surface-modified NMC by coatings such as Al2O3. In addition, while the dehydrogenation of solvents was observed in 1 M electrolytes with different anions, they were not observed on NMC811 in the concentrated electrolyte (EC/EMC with 3.1 M LiPF6), indicating lithium coordination could suppress dehydrogenation. Dehydrogenation of carbonates on NMC811 accompanied with rapid growth of interfacial impedance with increasing voltage revealed by electrochemical impedance spectroscopy (EIS), while the electrode–electrolyte combinations without dehydrogenation did not show significant impedance growth. Therefore, minimizing carbonate dehydrogenation on the NMC surface by tuning electrode reactivity and electrolyte reactivity is critical to develop high-energy Li-ion batteries with long cycle life.
In this paper, some electronic properties such as the electronic density of states (DOS), and energy band structure, and optical properties of the bulk and monolayer PtSe2 structure have been investigated based on the density functional theory (DFT) using full-potential linearized augmented plane wave (FP-LAPW) method and the modified Becke-Johnson potential (mBJ). By changing the PtSe2 structure size from bulk to monolayer, there have been major changes in the electronic (DOS and band structure) and optical properties such as the dielectric function. The electronic results show that PtSe2 in the bulk state exhibits a metallic property, while its nanosheet state, PtSe2 is a semiconductor with an energy gap of about 1.5 eV. Band structure calculations showed that for PtSe2 structure in the bulk state the energy distance between Γ-point and the K-point is about 0.4 eV, so it is concluded that PtSe2 is a semi-metal. The optical properties results show that the largest damping region for electromagnetic waves for a bulk PtSe2 structure in the z-direction is equal to 14.02 eV. The volume plasmon energy of the PtSe2 monolayer is smaller than the plasmon energy of the bulk PtSe2. Also, the optical reflectivity of the bulk PtSe2 is larger than the optical reflectivity of the PtSe2 monolayer.
Studies on neural and behavioral correlates of the serotonin transporter gene polymorphism (5-HTTLPR) strongly suggested interaction effects between the 5-HTTLPR genotype and environmental conditions on infant emotionality development. However, empirical studies that involve human infants are rare. The present study thus analyzed the interaction of the 5-HTTLPR genotype with the quality of maternal parenting behavior on the development of negative emotionality and fear in infancy. In a sample of 69 healthy firstborn infants, negative emotionality and fear were assessed at 4, 8, and 12 months using a multi-method approach. The quality of previous parenting has been operationalized as the quality of the mother–infant attachment relationship measured by the strange situation procedure at 18 months. Corresponding to hypotheses, to their caregiver insecurely attached infants who were homozygous for the s-variant of the 5-HTTLPR genotype developed a high level of negative emotionality and fear. The results thus are in line with the experimental results in the non-human primate model and point to a more pronounced susceptibility of s/s carrying infants to early rearing experiences.
This study examined Mn source effects on the electrochemical properties of Fe-substituted and Ni-substituted Li2MnO3 (Li1+x(Fe0.2Ni0.2Mn0.6)1−xO2, 0 < x < 1/3). Manganese sources of two kinds were selected: MnCl2·4H2O and KMnO4. Given the same preparation conditions, the chemical composition, transition metal distribution, and electrochemical properties of the two samples were compared. The sample obtained from KMnO4 exhibited better electrochemical performance, except for high-rate discharge characteristics, than that obtained from MnCl2. The origin of the different electrochemical performance was discussed to ascertain the unknown factor responsible for it. The full-cell performance was assessed using a single-layer laminate cell and mesocarbon microbead (MCMB) anode.
The aim of this paper is to evaluate the thermo-mechanical behavior of a multilayer section of a lithium-ion 18650 cell during discharge. Discharging experiments with the measurements of voltage, current output and surface temperature were conducted. The model, developed in the framework of macroscopic approach, accounts for the heat generation during the battery discharge as well as the thermal expansion of each material layer of the jelly roll and can. For sake of simplicity, the mechanical behavior is assumed linear elastic and isotropic, the layers are perfectly tied and the model does not include the lithiation expansion. However, the approach helps to point out the evolution of stresses at the interfaces of the multilayer assembly during complete discharge. It introduces the question of interface cohesion/contact ageing as cycling repeats.
A novel Li4Ti5O12 (LTO) electrode with a hierarchical carbon-based conducting network has been developed for high rate lithium ion battery. The unique network is constructed by graphene sheets (GS) that are not only dispersed among (inter-) but also inside (intra-) LTO particles, together with a thin carbon layer wrapping around the LTO particles. The intraparticle GS promotes the electron transfer inside LTO particles while the interparticle GS together with carbon coating bridges the particles guaranteeing fast electron transfer among LTO particles, which construct a highway throughout the whole electrode sheet. Quantitatively, only a trace amount of GS (∼ 0.4 wt%) synergistic with carbon coating (∼0.8 wt%) contributes to a more effective conducting network in the produced LTO electrode and as a result much better performance as compared to the LTO case with similar carbon coating but free of GS. Due to the effectiveness of the conducting network, even with a tap density as high as ∼1.0gcm−3, the novel LTO possesses both excellent rate performance and cycling behaviors. The capacity of 123.5mA h g−1 is obtained at a charge/discharge rate as high as 30C and a very high capacity of 144.8 mAh g−1 is maintained even after 100 cycles at 10C. Due to such a low fraction of carbon and a high tape density, the novel LTO electrode has a great practical application value in both the power and energy storage lithium ion batteries.
In lithium-ion batteries, ZnFe2O4 as an anode has attracted wide attention due to high theoretical capacity. However, volume expansion of ZnFe2O4 during charging and discharging limits its commercial application. ZnFe2O4 is synthesized by one-step solvothermal method and subsequent heat-treatment process. Polypyrrole (PPy) prepared by chemical oxidation polymerization is in-situ coated onto the surface of spherical ZnFe2O4 to form ZnFe2O4@PPy, and used to enhance electronic conductivity and electrochemical performance of ZnFe2O4. This core-shell structure alleviates effectively volume expansion during charging and discharging, and accelerates movement of lithium ions and electrons, thus ZnFe2O4@PPy possesses good electrochemical performance with the discharge capacities of 1182 mAh g−1 at a current density of 200 mA g−1 after 100 cycles and 906 mAh g−1 at 2000 mA g−1 after 500 cycles.