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High power lithium-ion batteries need to exhibit long service life to meet targets of automotive applications. This article describes the deep investigation of the so-called VL6P cells, high power lithium-ion cells mass produced by Johnson Controls – Saft (JC-S), in order to understand the root causes of their aging. Cells aged by calendar and cycle life are investigated here compared to fresh cells. Among the results of the different analyses, the most significant is that more active lithium is detected in negative electrode after aging. This tends to indicate that effect of aging is due to increase of positive electrode limitation. Results of this investigation will allow JC-S to continue to improve life of the lithium-ion cells.
Confined ZrO2 encapsulation over high capacity spinel-layer-layer structured 0.5Li[Ni0.5Mn1.5]O4·0.5 [Li2MnO3·Li(Mn0.5Ni0.5)O2] with various concentration by sol-gel process is reported. Presence of homogeneous ZrO2 layer is evident from the TEM studies. Various electrochemical studies such as optimization of ZrO2 concentration followed by rate performance, elevated temperature studies, and potential windows are also performed. Among the studies, 1wt.% ZrO2 modification is found superior in 2 − 4.9V vs. Li region compared to rest of the coating concentration and pristine compound. Cyclic voltammetry and impedance studies are also performed to understand the reaction mechanism and other electrochemical aspects.
Disruption of disrupted-in-schizophrenia 1 (DISC1), a candidate susceptibility gene for schizophrenia, was first identified in a large Scottish family in which many members suffered from various psychiatric disorders, including schizophrenia. To model the Scottish DISC1 truncation, we established a Disc1 mutant mouse line in which the 129S6/SvEv 25-bp deletion variant was transferred into the C57BL/6J strain by backcrossing. A battery of behavioral tasks was conducted to evaluate the basic behaviors and cognitive function of these mice. In heterozygote and homozygote Disc1 mutant (Het and Homo) mice, behavioral impairments were noted in working memory test which is thought to be mediated by the function of the medial prefrontal cortex (mPFC). The properties of mPFC neurons were characterized in both morphological and physiological aspects. The dendritic diameters were decreased in layer II/III mPFC pyramidal neurons of Het and Homo mice, whereas a significant reduction in spine density was observed in Homo mice. Neuronal excitability was declined in layer II/III mPFC pyramidal neurons of Het and Homo mice, yet increased transmitter release was identified in Homo mice. Thus, the structural and functional alterations of the mPFC in Het and Homo mice might account for their cognitive impairment. Since most of the gene knockout mice are generated from 129 substrain-derived embryonic stem cells, potential Disc1 deficiency should be considered.
The influences of the polytetrafluoroethylene (PTFE) content in silver-based gas diffusion electrodes on the resulting physical properties and the electrochemical performance during oxygen reduction in concentrated sodium hydroxide electrolyte were investigated through half-cell measurements. A systematic variation of the pore system was achieved by application of different silver/PTFE ratios during the production of the gas diffusion electrodes (GDE). In all electrodes, a silver skeleton structure with relatively constant properties was formed, while the PTFE fills up part of the open pore space. The resulting structures were characterized with a variety of methods for the physical properties supported by focused ion beam milling and scanning electron microscope (FIB/SEM) tomography. It could be shown that variations in the obtained pore system strongly influence the electrochemical performance of the electrodes. Determination of the Tafel slopes revealed that this is not due to changes in the electrocatalytic activity but rather caused by variations in the electrolyte uptake. While too small amounts of PTFE (1 wt%) lead to decreased performance through electrolyte flooding, higher PTFE contents above about 5 wt% also deteriorate the electrode performance because the extent of the three-phase boundary diminishes. The decisive role of the electrolyte intrusion was confirmed by measurements at higher electrolyte pressure. While the best electrochemical performance was achieved with an electrode containing 98 wt% silver, a slightly higher PTFE content is advisable to prevent breakthrough of the electrolyte.
Lithium metal is considered as the ultimate anode material for high-energy Li battery systems. However, the commercial application of lithium anode is impeded by issues with safety and low coulombic efficiency induced by Li dendrite growth. Herein, a free-standing three-dimensional nitrogen-enriched graphitic carbon sponge with a high nitrogen content is proposed as a multifunctional current collect for Lithium accommodation. The abundant lithiophilic N-containing functional groups are served as preferred nucleation sites to guide a uniform Li deposition. In addition, the nitrogen-enriched graphitic carbon sponge with a high specific surface area can effectively reduce the local current density. As a result of the synergistic effect, the nitrogen-enriched graphitic carbon sponge electrode realizes a long-term stable cycling without dendrites formation. Notably, the as-obtained composite electrode can deliver an ultra-high specific capacity of ∼3175 mA h g−1. The nitrogen-enriched graphitic carbon sponge might provide innovative insights to design a superior matrix for dendrite-free Li anode.
Objective This study compared the results of combined and individual ocular vestibular-evoked myogenic potential (oVEMP) and cervical VEMP (cVEMP) tests in healthy subjects and patients with unilateral vestibular hypofunction to confirm the effectiveness of the combined oVEMP and cVEMP test. Methods Twenty healthy volunteers and 12 patients with unilateral vestibular hypofunction underwent individual oVEMP and cVEMP tests in a random order, and combined oVEMP and cVEMP test on another day. Results Twenty healthy subjects had 100% response rates for oVEMPs and cVEMPs in both individual and combined stimulation modes. Significant positive correlations exist between individual and combined oVEMPs/cVEMPs in terms of latencies and amplitudes. In 12 patients with unilateral vestibular hypofunction, differences in abnormal percentages of oVEMPs or cVEMPs were non-significant. Additionally, the characteristic parameters of oVEMP/cVEMP among ears of healthy subjects, good and pathological ears of patients with unilateral vestibular hypofunction did not differ significantly, regardless of whether the individual or combined mode was used. Conclusions The combined oVEMP and cVEMP test generates similar information to that obtained by individual mode, regardless of whether subjects are healthy or have unilateral vestibular hypofunction. Significance Simultaneous oVEMP and cVEMP tests may be a convenient screening tool for assessing crossed vestibulo-ocular reflex and ipsilateral sacculo-collic reflex, which definitely shortens the diagnostic test time. Thus, it may favor the large diffusion of these techniques.
Electrocytes from the electric organ of Electrophorus electricus exhibited sodium action potentials that have been proposed to be repolarized by leak currents and not by outward voltage-gated potassium currents. However, patch-clamp recordings have suggested that electrocytes may contain a very low density of voltage-gated K+ channels. We report here the cloning of a K+ channel from an eel electric organ cDNA library, which, when expressed in mammalian tissue culture cells, displayed delayed-rectifier K+ channel characteristics. The amino-acid sequence of the eel K+ channel had the highest identity to Kv1.1 potassium channels. However, different important functional regions of eel Kv1.1 had higher amino-acid identity to other Kv1 members, for example, the eel Kv1.1 S4-S5 region was identical to Kv1.5 and Kv1.6. Northern blot analysis indicated that eel Kv1.1 mRNA was expressed at appreciable levels in the electric organ but it was not detected in eel brain, muscle, or cardiac tissue. Because electrocytes do not express robust outward voltage-gated potassium currents we speculate that eel Kv1.1 channels are chronically inhibited in the electric organ and may be functionally recruited by an unknown mechanism.
Exfoliated graphite nanoplatelet (xGnP) and V2O5 nanotube (VNT) composite electrodes were fabricated and tested as electrodes for supercapacitors. Enhancement of the electrochemical performance of the composite over its component materials was demonstrated using cyclic voltammetry (CV), constant current charge/discharge testing and electrochemical impedance spectroscopy in aqueous and organic electrolytes. The calculated specific capacitance of the composite was 35Fg−1 in the aqueous electrolyte and 226Fg−1 in the organic electrolyte at a scan rate of 10mVs−1 using a three-electrode system. Asymmetric coin cell devices were fabricated using activated carbon cloth as the positive electrode and xGnP–VNT composite as the negative electrode. The energy and power densities in 1M LiTFSI were 28Whkg−1 and 303Wkg−1, respectively, at a discharge current density of 250mAg−1.
It is still a great challenge to improve the diffusion dynamics of Na+ throughout the Na3V2(PO4)3, one of the most promising cathodes for sodium ion batteries. In this work, we present a facile doping strategy to tackle this problem by co-doping the Na+ with K+ and Ca2+. Na3-3xKxCaxV2(PO4)3/C (x = 0, 0.05, 0.07 and 0.09) composites are prepared by a sol-gel method combined with freeze-drying and high-temperature calcination processes, and the composites are characterized by XRD, XPS, SEM, TEM and electrochemical measurements. The results indicate that co-substitution of K+ and Ca2+ for Na in Na3V2(PO4)3 enlarges the cell volume of Na3V2(PO4)3 and is beneficial for improving electrochemical performance. All co-doped Na3V2(PO4)3/C composites have better electrochemical performance than the pristine Na3V2(PO4)3/C composite. The optimal doping compositions are found to be Na2.79K0.07Ca0.07V2(PO4)3/C, displaying reversible capacities of 110.2, 92.7 and 83.6 mAh·g-1 at the current densities of 0.1, 1, and 10C (1180 mA·g-1), respectively, in the voltage range of 2.5–4.0 V. The Na2.79K0.07Ca0.07V2(PO4)3/C exhibits capacity retentions of 91% at 1C after 50 cycles and 83% at 10C after 150 cycles, while Na3V2(PO4)3/C composite displays capacity retentions of 88.5% at 1C after 50 cycles and 26.5% at 10C after 150 cycles, respectively. The improved electrochemical performance of co-doped Na3V2(PO4)3/C is ascribed to enhanced Na+ diffusion after the co-substitution of K+ and Ca2+ for Na in Na3V2(PO4)3/C.
Electrical and thermal characteristics of lithium-ion battery packs in electric vehicles in different operating conditions are important in order to design the battery pack thermal management system. In this work, electrical and thermal behaviors of different size of LiFePO4 cylindrical cells are investigated under various operating conditions. The simulation results show good agreement with the experimental data under various operating modes. Due to the large thermal resistance of layered active material in a Li-ion cell, the temperature difference in the radial direction is significantly correlated with a diameter of cell and It -rates. Compared with natural convection, strong forced convection will reduce the temperature uniformity in the cell and accelerate the thermal aging rate. Lastly, integration issues of the cells into a battery pack are discussed from mechanical, electrical, thermal, control and monitoring, manufacturing and maintenance aspects. These issues could impact the performance, cost, driving range and life cycle of the battery pack in electric vehicles.
In the present study, poly(ethylene oxide) (PEO)-based polymeric composite electrolytes (PCEs) had been prepared by using a different content of mesoporous silicate MCM-41, in order to examine the filler addition effect on the microstructural and electrochemical properties. The interactions between MCM-41 and PEO matrix were studied by XRD, DSC, and SEM techniques. The electrochemical properties of the PCEs, such as ionic conductivity, its temperature dependence, and lithium transference number were investigated. MCM-41 could maintain the pore structure effectively, resulting in nanocomposites that were homogeneously complexed with the PEO chains. The PCEs with 8wt.% MCM-41 showed the smallest crystallinity, 30.4%. Accordingly, those PCEs showed the highest ion conductivity, 1.2×10−4 S/cm, a two-order-of-magnitude higher value than that of the pristine PEO–LiClO4. This might have reflected decreased crystallinity and improved ion transport. Furthermore, those PCEs showed an increased Li ion transference number of ∼0.5. In conclusion, the filler addition could enhance the ionic conductivity and increase the Li ion transference number at the same time.
In an effort to develop a useful electrolyte for a Li-ion cell applicable in a wide operation temperature, we have studied a number of ternary electrolytes containing a cyclic carbonate (ethylene carbonate (EC)), a linear carbonate (dimethyl carbonate (DMC), diethyl carbonate (DEC), or ethylmethyl carbonate (EMC)), and a low-temperature freezing solvent (methyl acetate, ethyl acetate, isopropyl acetate, isoamyl acetate, or ethyl propionate (EP)). We have studied performance including cycle life of Li-ion cells containing these electrolytes at various temperatures. The performance was various with various electrolyte compositions showing a significant effect of the low-temperature freezing solvents while the effect of the linear carbonates was relatively minor. Cells containing an electrolyte of EC–DMC–MA showed an excellent initial performance at −20°C but it did not give a good cycle life compared with others. Two electrolyte compositions containing EP, EC–DEC–EP and EC–EMC–EP, showed the most attractive overall performance including initial performance at −20°C, cycle life and rate capability at room temperature as well as 50°C.
Microglass separators have been used in lead-acid batteries for more than 20 years with excellent results. This type of separator (known as recombinant battery separator mat (RBSM)) has allowed valve-regulated lead-acid (VRLA) battery technology to become a commercial reality. When the concept of the VRLA battery was developed, the requirements of the RBSM separator were not fully known nor appreciated. In many cases, the direction charted for the separator has not been the most beneficial path to follow for separator performance and battery life. In some cases, such as the density of the separator media, experience has shown that the most correct path (low density) does not give rise to long battery life. As VRLA battery technology matures, greater pressure on cost and quality has arisen, especially with the proposed transition to 42V automotive applications. This paper reviews some of the advances and changes in the RBSM separator made over the last 20 years, and provides some thoughts on future directions for this essential component of the VRLA battery.
A unique requirement of underwater vehicles' power/energy systems is that they remain neutrally buoyant over the course of a mission. Previous work published in the Journal of Power Sources reported gross as opposed to neutrally-buoyant energy densities of an integrated solid oxide fuel cell/Rankine-cycle based power system based on the exothermic reaction of aluminum with seawater. This paper corrects this shortcoming by presenting a model for estimating system mass and using it to update the key findings of the original paper in the context of the neutral buoyancy requirement. It also presents an expanded sensitivity analysis to illustrate the influence of various design and modeling assumptions. While energy density is very sensitive to turbine efficiency (sensitivity coefficient in excess of 0.60), it is relatively insensitive to all other major design parameters (sensitivity coefficients < 0.15) like compressor efficiency, inlet water temperature, scaling methodology, etc. The neutral buoyancy requirement introduces a significant (∼15%) energy density penalty but overall the system still appears to offer factors of five to eight improvements in energy density (i.e., vehicle range/endurance) over present battery-based technologies.
Aim of the study The wound healing properties of jojoba (Simmondsia chinensis) liquid wax (JLW) were studied in vitro on HaCaT keratinocytes and human dermal fibroblasts, which are involved in wounded skin repair. Materials and methods JLW cytotoxicity was evaluated by the crystal violet staining and the neutral red uptake endpoint. Induction of wound healing by JLW was assessed by scratch wound assay on cell monolayers. The involvement of signaling pathways was evaluated by the use of the Ca2+ chelator BAPTA and of kinase inhibitors, and by Western blot analysis of cell lysates using anti-phospho antibodies. Collagen and gelatinase secretion by cells were assayed by in-cell ELISA and zymography analysis, respectively. Results Cytotoxicity assays showed that the toxic effects of JLW to these cells are extremely low. Scratch wound experiments showed that JLW notably accelerates the wound closure of both keratinocytes and fibroblasts. The use of inhibitors and Western blot revealed that the mechanism of action of JLW is strictly Ca2+ dependent and requires the involvement of the PI3K–Akt–mTOR pathway and of the p38 and ERK1/2 MAPKs. In addition, JLW was found to stimulate collagen I synthesis in fibroblasts, while no effect was detected on the secretion of MMP-2 and MMP-9 gelatinases by HaCaT or fibroblasts. Conclusions Taken together, data provide a pharmacological characterization of JLW properties on skin cells and suggest that it could be used in the treatment of wounds in clinical settings.
To improve the performance of rechargeable lithium-ion batteries, a microscopic understanding of the electrochemical reaction at the cathode is necessary. The spatial distribution of the electrode redox reaction for the LiFePO4 cathode was analyzed by X-ray absorption fine structure (XAFS) imaging. Chemical state maps of the planar cathode electrode obtained by the in situ XAFS imaging revealed the inhomogeneity of the chemical state of Fe during the charge/discharge process. The chemical state maps for the reverse charge/discharge process demonstrated the reversibility of the inhomogeneous distribution. The in-plane radial progress of the reaction distribution strongly suggests that the inhomogeneous electrode reaction is caused by the difference in electrical conductivity; the charging and discharging reactions proceed through reaction channels with low electrical resistance in the cathode.
Si has attracted enormous research and manufacturing attention as an anode material for lithium ion batteries (LIBs) because of its high specific capacity. The lack of a low cost and effective mechanism to prevent the pulverization of Si electrodes during the lithiation/delithiation process has been a major barrier in the mass production of Si anodes. Naturally abundant gum arabic (GA), composed of polysaccharides and glycoproteins, is applied as a dual-function binder to address this dilemma. Firstly, the hydroxyl groups of the polysaccharide in GA are crucial in ensuring strong binding to Si. Secondly, similar to the function of fiber in fiber-reinforced concrete (FRC), the long chain glycoproteins provide further mechanical tolerance to dramatic volume expansion by Si nanoparticles. The resultant Si anodes present an outstanding capacity of ca. 2000mAh/g at a 1C rate and 1000mAh/g at 2C rate, respectively, throughout 500 cycles. Excellent long-term stability is demonstrated by the maintenance of 1000mAh/g specific capacity at 1C rate for over 1000 cycles. This low cost, naturally abundant and environmentally benign polymer is a promising binder for LIBs in the future.
Using a microwave-assisted path, MnO2 structures were prepared to be used as catalyst material in room-temperature-operated sodium-air cells. The electrochemical cells are prepared using a dry coating step (Laser Induced Forward Transfer), i.e. without organic solvents. Due to a novel formulation for an electrolyte, the electrochemical stability and performance of as-prepared electrodes is very high (1215 Ah/kg specific charge).
In the present work, a novel pyranose ring laden polymer electrolyte is proposed for all solid Na-ion secondary cells that can operate at moderate temperatures. The prepared fully solid polymer electrolyte film is based on a classic polyethylene oxide (PEO) backbone, homogeneously blended with sodium carboxymethyl cellulose (Na-CMC) and sodium perchlorate. The favourable use of Na-CMC as electrode binder as well as electrolyte additive is evaluated, which would enhance the pathways for forming an optimised electrode/electrolyte interface. The promising prospects of the newly elaborated hybrid electrolyte are investigated by means of galvanostatic charge/discharge cycling in lab-scale cell with TiO2-based or NaFePO4-based working electrodes.
Mesoporous LixMnO2 cathode material is synthesized using the one-pot anodic electrodeposition through simultaneous electrodeposition and Li+ incorporation into the host manganese dioxide without using of any template. Incorporating Li+ into the manganese oxide structure definitely influences the properties of the final material. The content of incorporated Li+ in the manganese dioxide structure (x in LixMnO2, x=0.07–0.33) is determined as a function of Li+ concentration in the electrodeposition bath. The various contents of Li+ in LixMnO2 samples have a tremendous impact on the ultimate material in terms of structural and physicochemical properties. The structural changes of host manganese dioxide as a consequence of Li+ intercalation have been identified through the X-ray diffraction, inductively coupled plasma-optical emission spectroscopy, Fourier-transform infrared, thermogravimetric/differential scanning calorimetry as well as Raman spectroscopy. The results of nitrogen adsorption-desorption isotherms along with the scanning electron microscopy proved the mesoporous structure of electrode materials with a significantly high surface area. Among the LixMnO2 materials, the Li0.21MnO2, shows the best electrochemical performance with the first discharge capacity of 283.0, 240.0, 191.0,161.0 and 113.0mAhg−1 at 0.1C, 0.2C, 1C, 2C and 5C, respectively, retaining 92% of the initial capacity over 50cycles at 0.1C.
In this study, the N-hydroxyalkyl derivatives of pyrrole (Py), N-(2-hydroxyethyl)pyrrole (HE) and N-(3-hydroxypropyl)pyrrole (HP), were synthesized. The corresponding homopolymers, PHE and PHP, together with the copolymers of Py/HE and those of Py/HP were prepared by galvanostatic polymerization. These monomers and polymers were characterized by FTIR spectroscopy, elemental analysis, SEM and electrochemical techniques. The result of potential–time profiles showed that a higher potential was required for HE and HP than Py for the polymerization. This was ascribed to the steric hindrance of high concentration of the N-hydroxyalkyl groups. However, a similar potential was observed for the copolymerization of Py/HE and Py/HP systems as that of Py due to the reduction of the steric effect by lower content of the substituent. The SEM micrographs showed a rougher morphology for the films synthesized from the solutions with higher Py/derivatives ratio. The cyclic voltammograms indicated that all the copolymers were larger, while the homopolymers had smaller anodic/cathodic currents and specific charges than PPy. This implied that the existence of the proper amount of the N-hydroxyalkyl pendant groups enhanced the ionic mobility of the pyrrole polymers. The results of charge/discharge measurements showed that the copolymer PYHP82 has the highest discharge capacity among the pyrrole polymers prepared.