Intermediate Discharge Research Articles

Strontium stannate as an alternative anode for Na- and K-Ion batteries: A theoretical study

Theoretical predictions on structural, electronic and transport properties of pristine and alkali-doped strontium stannate (SrSnO3) were made using density functional theory and force field methods. Results of electronic structure computations show that a doping of alkali-ion (Li+, Na+ and K+) into SrSnO3 induces the apparition of extra energy bands on the valence and conduction bands and small translation of the valence and conduction band limits. This is more accentuated in K+-ion doped samples with lower energy gap. Defect energetics computations reveal a low energetic cost associated the alkali incorporation mechanism proposed in this work. Such a mechanism provides us with an intermediate first discharge reaction to describe the delithiation process. Results on alkali ion transport properties in interstitially doped nanocrystalline SrSnO3 samples reveal lower diffusion activation energies of 0.25, 0.28 and 0.44 eV and diffusion coefficient at 25 °C of 9.6, 2.9 × 10−11 and 4.8 × 10−13 cm2s−1 for Li-, Na- and K-doped samples, respectively. These predicted properties bring in new evidence to stimulate a consideration of strontium stannate for use as an alternative anode, in particular for both Na- and K-ion batteries.

Studies on Highly Conducting Graphene in Sulfur Composite Cathode for High Energy Lithium Sulfur (Li-S) Battery

The rapid increase in the global energy consumption and the environmental impact of traditional energy resources has led to tremendously increased research activities on clean and renewable energy sources during last decade. The sulfur and graphene composite cathode materials have great potential in improving the overall electrochemical performance of lithium ions rechargeable batteries.Sulfur cathodes generally suffer from fast capacity degradation and poor Coulombic efficiency originating from the dissolution of intermediate discharge products in the electrolyte. The polysulfide dissolution causes loss of active sulfur, which deteriorates electrochemical performances at low cycling rates. To enhance the electrochemical performance of sulfur highly conducting graphene has been dispersed in sulfur. Here we report a study on graphene-sulfur (S1-x Gx where x=0.1, 0.2, 0.3 &0.4 etc.) composites as a cathode fabricated by ball-milling technique for lithium sulfur batteries. The characterization of the composites has been performed by X-ray diffraction (XRD), scanning electron microscopy (SEM), and RAMAN spectroscopy. The electrochemical performance of graphene-sulfur composite cathodes has been found to be enhanced and stable at deep charge-discharge. The high-capacity behavior through redox reactions occurs on surface and throughout the bulk. The major drawback of sulfur cathode is the dissolution in electrolyte while intercalation and de-intercalation of Li ions resulting in a low cycling stability in Li-S batteries and the electrochemical studies will be presented in detail.

A morphological and textural analysis of Inconel-718 aerospace alloy processed through electrical discharging machining

The Inconel 718 has captured global attention for its huge applications in the aerospace and defense field. However, a limited approach is noticed to investigate this material's responses and morphological features after electrical discharge machining operation. This study wants to offer a more detailed investigating approach, including the analysis of morphological features, recast layer, microhardness, elemental composition, and several textural defects and basic responses. Scanning electron microscopy is used to investigate several textural features, defects, cracks, and recast layers. The findings claim 538 nm–2.168 µm and 14–41 µm variations in crack width and recast thickness, respectively, which increase with pulse current and pulse on-time. However, the low discharge energy can provide better micro-hardness than higher discharge conditions due to having sufficient time for flushing and heat dissipations. The recast surface and the interfaces are, respectively, 7.58%–13.16% and 22.75%–32.74% harder with low discharge condition than the intermediate and higher discharge condition. Moreover, the Energy Dispersive X-ray analysis reported the emigration of 17.81% of carbon and 0.33% of copper from the dielectric and tool during the machining.

Nano storage-boxes constructed by the vertical growth of MoS2 on graphene for high-performance Li-S batteries

In order to accelerate the reaction kinetics of lithium-sulfur batteries, the introduction of electro catalysis and proper structural control of the sulfur cathode is urgently needed. MoS2 nano sheets was selectively grown vertically (V-MoS2) on the microwave-reduced graphene (rGO) sheets through chemical coupling to construct a self-supporting sulfur cathode with a nano storage-box structure (V-MoS2 as the wall and rGO as the bottom). RGO, which has a high conductivity of 37 S cm−1, greatly accelerates the transfer of electrons from the active sites on the edge of the layer to the solution. The introduction of carbon tubes can connect the abundant pores in the foam and act as a long-range conductive path. The 2D-orthogonal-2D structure maximally exposes the edge active sites of MoS2, and together with graphene form a nano reactor of sulfur, intermediate lithium polysulfides and discharge product Li2S(2). The effective combination of the microstructure confinement of the nano storage-boxes and the efficient synchronous catalytic mechanism of V-MoS2 greatly improves the electrochemical performance of the lithium-sulfur batteries. As a result, the assembled lithium-sulfur battery displays a high initial discharge capacity of 1379 mAh g−1, good cycle stability (86% capacity retention after 500 cycles at 0.1C) and superior rate performance.

Design of Information Acquisition System for High Voltage Pulse Power Supply

Capacitor discharge is the main application form of pulse power technology, which is simple in principle and easy to implement. The design of pulse power supply system requires the information management of a large amount of experimental data. While the conventional acquisition system only pays attention to the display of the power waveform, and lacks the effective management of the intermediate state information and discharge waveform, which cannot meet the requirement of power supply. Aiming at this need, an integrated power supply information acquisition system based on Labview and Access database is designed. This system takes Labview as the software development platform and Access as the background database to realize the acquisition, storage and information management of power data. In the program design, the producer-consumer mode is adopted for data collection and processing, and the queue technology is used for circular communication to ensure the integrity and reliability of data processing. The actual operation shows that the acquisition process of the system is stable and reliable, and the information management of the power data is realized.

Effectiveness and outcomes of invasive species removal in Hawaiian streams

Despite aquatic invasive species (AIS) being a widely recognized threat to native biodiversity in streams on subtropical and tropical oceanic islands across the Pacific, AIS management has been constrained by concerns that methods of removal could result in more harm than good. In this study, we assessed the effectiveness and outcomes of combining hand-netting and streamside sequestration of native species with AIS removal via three-pass electrofishing tailored for Hawaiian Island watersheds. Removals were conducted in 13 watersheds on the island of O‘ahu following a before-after, control-impact design to assess how AIS removal and post-removal community reassembly varied by surface flow and target species of interest. We found that removals resulted in a sharp reduction in AIS densities without altering native species densities. Removal efficacy was greatest in streams with intermediate mean discharge irrespective of target group or pre-removal AIS densities. Long-term monitoring demonstrated that removals led to persistent shifts in community composition reflecting sustained reductions in AIS densities. These findings indicate that electrofishing can be a valuable tool for AIS management in Hawaiian and other subtropical Pacific island streams, so long as steps are taken to minimize potential harm to at-risk and culturally important native species.

Analysis of water level variations in the Huangzhuang reach (Hanjiang River, China) during recent years

Abstract. The 2017 Hanjiang autumn flood appeared to have higher surface water levels at the same discharge rate than previously at the Huangzhuang gauging station. It is seriously impacted the flood control. This paper analyses the 2000–2017 data from the Huangzhuang reach in the Hanjiang River, including surface water levels, the surface water fall, erosion-deposition variation and the engineering activities. A comparison of the 2016–2017 data with the 2000–2015 data in the Huangzhuang reach, revealed that the surface water levels were about 1.47 and 0.13 m higher in the high and intermediate discharge ranges, respectively. In the low discharge range, the 2016–2017 and 2010–2015 surface water levels were similar. However, a comparison of the 2016–2017 with the 2000–2009 data in the low discharge range, shows that the surface water levels were 0.28–0.4 m lower. The surface water fall in the Zhuandouwan–Huangzhuang's reach decreased in 2016–2017 for discharges above 5000 m3 s−1, whereas in the Huangzhuang–Datong reach the opposite was found. For other time periods and discharge ranges the fall decreased. In the Datong-Shayang reach the fall reduced in 2014–2015 relative to other periods in 2000–2017 in the discharge range above 5000 m3 s−1. The erosion-silting analysis for the Huangzhuang reach showed scouring of local river deposits due to bridge engineering. However, near the bridge the substantial silting was found. The collated surface water level and scouring-silting data suggest that reduced surface water levels during low discharge are mainly due to the overall river erosion. The increased surface levels in the high discharge range are due to local river siltation, especially because of the increased water resistance as response to bridge engineering.

Increased arc length and stability in a magnetic gliding arc discharge using a cylindrical notched cathode

Intermediate arc discharge plasmas allow for working with ions at lower temperatures than thermal plasmas and can generate greater selectivity in certain chemical reactions due to the high vibrational and electron temperature. In this paper, a magnetic gliding arc discharge (MGA), which is an intermediate plasma, was developed and is described. The reactor is operated with CO2 as the working gas, but open to atmosphere. It presents increased arc length and stability by using a cylindrical notched cathode (CNC). The constructed rectangular section of the notch channel on the cylindrical cathode surface allowed the arc to be confined within the channel with enhanced stability. The changes in the cathode geometry allowed the system to reach radial arc length of 40 mm, plasma disc diameter of 102 mm, and from 300 to 400 mA of current. A low cost electro-optical device was set up to determine the arc rotation frequency and is described in detail. Measurements of frequency (f) as a function of current (I) indicates that the developed MGA-CNC follows the relation f∝ I0.5, which agrees with the theoretical prediction. In order to compare the MGA-CNC data acquired with other reported MGAs, an analysis considering the distinct magnetic field intensities (Br) and different cathode diameters (D) was performed. Thus, a linear relationship was observed for f D/(Br=D/2)1/2 as a function of I1/2, which may represent the general experimental behavior of different MGA operated in air at atmospheric pressure. The arc diameter (d) in the region near the cathode (at r = D/2) can be determined from the slope α of the plot (α = 6.03 m kg−1/2); the obtained value (d = 3.2 ± 0.7 mm) is coherent with measured values elsewhere.

Seed conditioning process in the sanitary quality of marandu grass seeds

The purpose of seed conditioning process is to separate seeds and their associated structures into different fractions and retain only good and healthy seeds. Thus, the aim of this study was to evaluate the effects the stages of seed conditioning have on the sanitary quality of marandu grass seeds. The seeds were sampled before and during the seed conditioning process, i.e., after exiting the air-screen cleaner and sieves (seeds discharged from the top, middle and bottom sieves), the first gravity separator (seeds drifting around the table, upper and intermediate discharge) and second gravity separator (upper, intermediate and lower discharge). The sanitary analysis was performed using the filter paper method with and without surface disinfestation of the seeds, which were incubated at 20±2°C, with a photoperiod of 12 hours for seven days. The experiment was conducted in a completely randomized design, in a 2x6 factorial scheme (surface disinfestation x stages of the seed conditioning process) and ten replications. The data was submitted to analysis of variance, using the F test and, when significant, the means of the treatments were compared using the Tukey test at 5% probability. It was concluded that it is not possible to improve the sanitary quality of marandú grass seeds through the seed conditioning process.

Temperature controls production but hydrology regulates export of dissolved organic carbon at the catchment scale

Abstract. Lateral carbon flux through river networks is an important and poorly understood component of the global carbon budget. This work investigates how temperature and hydrology control the production and export of dissolved organic carbon (DOC) in the Susquehanna Shale Hills Critical Zone Observatory in Pennsylvania, USA. Using field measurements of daily stream discharge, evapotranspiration, and stream DOC concentration, we calibrated the catchment-scale biogeochemical reactive transport model BioRT-Flux-PIHM (Biogeochemical Reactive Transport–Flux–Penn State Integrated Hydrologic Model, BFP), which met the satisfactory standard of a Nash–Sutcliffe efficiency (NSE) value greater than 0.5. We used the calibrated model to estimate and compare the daily DOC production rates (Rp; the sum of the local DOC production rates in individual grid cells) and export rate (Re; the product of the concentration and discharge at the stream outlet, or load). Results showed that daily Rp varied by less than an order of magnitude, primarily depending on seasonal temperature. In contrast, daily Re varied by more than 3 orders of magnitude and was strongly associated with variation in discharge and hydrological connectivity. In summer, high temperature and evapotranspiration dried and disconnected hillslopes from the stream, driving Rp to its maximum but Re to its minimum. During this period, the stream only exported DOC from the organic-poor groundwater and from organic-rich soil water in the swales bordering the stream. The DOC produced accumulated in hillslopes and was later flushed out during the wet and cold period (winter and spring) when Re peaked as the stream reconnected with uphill and Rp reached its minimum. The model reproduced the observed concentration–discharge (C–Q) relationship characterized by an unusual flushing–dilution pattern with maximum concentrations at intermediate discharge, indicating three end-members of source waters. A sensitivity analysis indicated that this nonlinearity was caused by shifts in the relative contribution of different source waters to the stream under different flow conditions. At low discharge, stream water reflected the chemistry of organic-poor groundwater; at intermediate discharge, stream water was dominated by the organic-rich soil water from swales; at high discharge, the stream reflected uphill soil water with an intermediate DOC concentration. This pattern persisted regardless of the DOC production rate as long as the contribution of deeper groundwater flow remained low (<18 % of the streamflow). When groundwater flow increased above 18 %, comparable amounts of groundwater and swale soil water mixed in the stream and masked the high DOC concentration from swales. In that case, the C–Q patterns switched to a flushing-only pattern with increasing DOC concentration at high discharge. These results depict a conceptual model that the catchment serves as a producer and storage reservoir for DOC under hot and dry conditions and transitions into a DOC exporter under wet and cold conditions. This study also illustrates how different controls on DOC production and export – temperature and hydrological flow paths, respectively – can create temporal asynchrony at the catchment scale. Future warming and increasing hydrological extremes could accentuate this asynchrony, with DOC production occurring primarily during dry periods and lateral export of DOC dominating in major storm events.

Investigating the Promise of Incorporating a Redox Mediator in Li–O2/CO2 batteries

In recent years, continuous studies have highlighted the languished research state of Li–O2, and the impelling development of energy storage devices with analogously high theoretical energy density [1]. In preliminary studies, we established that fed O2 and CO2 mixtures (Li–O2/CO­2) swiftly shift the reaction mechanism toward an exclusive formation of Li2CO3 in a TEGDME-based electrolyte. The proposed O2-assisted pathway is initiated by an electron transfer from the cathode, with subsequent CO4 – formation and complete Li2O2 suppression. Compared with O2-driven counterparts, the CO2-based Li–air cell suffers, however, from higher overcharges during the decomposition of Li2CO3 at ~4.5 V, rendering impracticable a commercialization of these technologies [2]. Here we propose for the first time the incorporation of a redox mediator (RM) toward facile Li2CO3 oxidation in Li–O2/CO­2 devices. Lithium bromide (LiBr) possessing two redox couples (Br−/Br3 − and Br3 −/Br2) has gathered increasing attention in conventional Li–air cells and was considered a suitable candidate in this study. All galvanostatic measurements were carried out under 30% CO2. At optimized concentrations, hindered recharge potentials (~0.5 V) at similarly sustained cyclability were demonstrated. Further dissection of the significance of involved Br−/Br3 −/Br2 species inferred, however, an additional role of the RM in the stabilization of intermediate discharge species and in the undesirable formation of side-products. In this context, drawn conclusions reinforced the need to consider a deeper evaluation of the effects of a RM inclusion beyond an overcharge decrease and the urge to stabilize RM/RM+ species participating in deleterious side-reactions with neighboring species and cell components.

Facet Engineering of Low-Cost Transitional Metal Oxides for Tunable ORR/OER Kinetics

To meet future needs for industries from personal devices to automobiles, energy storage devices are transitioning into the next-generation advanced battery systems beyond lithium ions with higher energy density. Among them, lithium-oxygen (Li-O2) battery stands out due to its highest theoretical energy density among all rechargeable ion battery systems. Yet, its application is severely disabled by the sluggish reaction kinetics during oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). To address this problem, various catalysts have been developed with the most promising materials being the noble metals (Pt, etc.) and transitional metal oxides (TMOs such as CoxOy, MnxOy, etc.). While the noble metal catalysts offer superior performance in terms of improving the reaction kinetics, the high cost and environmental sensitivity prevent the large-scale application. As an alternative, TMOs are attracting more and more interest because they exhibit satisfactory catalytic performance while their cost and cycling durability are much better than that of noble metals. While most studies have focused on the development of different TMO structures, phases and compositions, few studies have reported the advancement in the crystalline facet engineering, particularly for the low-cost TMOs such as manganese oxides, and its effect on ORR/OER kinetics. In this work, beta-(β-)MnO2 crystals with either octahedron or rod-like shapes were successfully synthesized separately using a simple hydrothermal method. Combining various electron microscopic methods, the octahedron’s surface is seen to mostly occupied by MnO2-{111} facets, while rod’s surface is occupied by MnO2-{100}. As the cathode for Li-air batteries, the β-MnO2 with {111} facets and {100} facets catalyzed the formation of Li2O2 into large toroids and thin film, respectively. For the first time, we revealed that the control of crystal facets can switch the Li2O2 formation mechanism from the surface mode to the solution mode even in the low donor number TEGDME electrolyte. To further understand the formation kinetics of Li2O2, we referred to operando liquid cell transmission electron microscopy, by which a LiO2 phase was identified to function as the intermediate discharge products which significantly affect the formation of Li2O2 as the final product. Following this finding, DFT results further showed that the different catalytic properties were due to the different adsorption free energies for the LiO2 intermediate on the {111} and {100} facets of MnO2. Our findings revealed that facet-engineering of the low-cost TMO catalysts would open a new way for the design of lithium-air batteries with high stabilities and long cycle life. Figure 1

Acute Venous Thromboembolism Risk Highest Within 60 Days After Discharge From the Hospital in Patients With Inflammatory Bowel Diseases

Patients with inflammatory bowel diseases (IBDs) have a high risk of venous thromboembolism (VTE). We assessed the timing and risk factors associated with readmission to the hospital for VTE among patients with IBD. We collected data from the Nationwide Readmissions Database on IBD index admissions resulting in readmission to the hospital for VTE within 60 days, from 2010 through 2014. We used univariable and multivariable regression to assess risk factors associated with VTE readmission with unadjusted risk ratio (RR) and adjusted RR (aRR) as measures of effect. Time to VTE readmission was assessed in 10-day intervals, for up to 90 days. We identified 872,122 index admissions of patients with IBD; 1160 resulted in readmission with VTE. More than 90% of readmissions occurred within 60 days of discharge from the index admission. Factors associated with hospital readmission with VTE included prior VTE, longer length of hospital stay, comorbidities, having a flexible sigmoidoscopy or colonoscopy at index admission, and age older than 18 years. Additional risk factors included Clostridium difficile infection at index admission (aRR, 1.47; 95% CI, 1.17-1.85) and discharge to a skilled nursing facility or intermediate care facility (aRR, 1.39; 95% CI, 1.14-1.70) or discharge with home health services (aRR, 1.65; 95% CI, 1.41-1.94). Among patients admitted to the hospital with IBD, most readmissions with VTE occur within 60 days of discharge. Readmission with VTE is associated with C difficile infection and discharge to a skilled nursing facility, intermediate care facility, or with home health services. Studies are needed to evaluate the potential benefit of extending VTE prophylaxis for patients admitted to the hospital with IBD for up to 2 months after discharge, to minimize risk.

A Tanks-in-Series Electrochemical Engineering Model for Lithium Sulfur Batteries

Lithium sulfur (LiS) batteries are promising for next-generation energy storage. Due to their high energy density, lithium sulfur batteries are attractive for applications like electric vehicles and electric flights where weight is an important constraint. However, LiS batteries suffer from low coulombic efficiency, poor cycle life, and self-discharge. ­­ 1 Physics-based models can give insight into the internal states of the battery, which can be correlated to the mechanisms that contribute to performance degradation under various operating conditions. The first one-dimensional electrochemical discharge model for LiS batteries was developed by Kumaresan et al. using porous electrode theory, and considers transport, kinetics, thermodynamics, and morphological changes.2 The LiS chemistry includes multiple charge carriers and morphology changes as discharge proceeds, which contributes to the complexity and challenges of accurate modeling. The corresponding physics-based model results in a complex and numerically stiff equation system with variables that change across orders of magnitude and require proper initialization. The mathematical complexity of such electrochemical models motivates the use of reformulation and simplification techniques in order to justify their use in estimation, control, and optimization. Even for fast reformulated models, the large number of kinetic and transport parameters resulting from the complex chemistry makes their parameterization a non-trivial task. Several groups have used lumped and one-dimensional models to simplify modeling and study specific characteristics, such as self-discharge, rate-dependence of precipitation, or charging.3–9 This work demonstrates a mass-conserving tank-in-series model based on the original model developed by Kumaresan et al.2 The tank-in-series model is developed through volume-averaging of the model equations. The volume averaging results in overall balance equations governing the evolution of average variables in each region of the cell. The elimination of the spatial dependence from model equations substantially increases computational efficiency and reduces the number of parameters to be estimated. Comparisons of the tank-model simulations with the full model indicate the ability of the averaged model to capture discharge behavior at low to intermediate discharge rates, with deviations mainly observed towards the end of discharge. Other advantages and limitations of this model as compared to the full model are characterized in terms of electrochemical variable predictions, with applications in control and estimation for hybrid electric flights. The model predictions are compared against experimental data from 19.5 Ah pouch cells and have been improved through estimation of parameters. Acknowledgments The authors are thankful for financial support from BAE Systems and the Joint Center for Aerospace Technology Innovation. References X. Zhang, H. Xie, C.-S. Kim, K. Zaghib, A. Mauger, and C. M. Julien, Mater. Sci. Eng. R Reports, 121, 1 (2017).K. Kumaresan, Y. Mikhaylik, and R. E. White, J. Electrochem. Soc., 155, A576 (2008).Y. V. Mikhaylik and J. R. Akridge, J. Electrochem. Soc., 151, A1969 (2004).K. Yoo, M.-K. Song, E. J. Cairns, and P. Dutta, Electrochim. Acta, 213, 174 (2016).Y. X. Ren, T. S. Zhao, M. Liu, P. Tan, and Y. K. Zeng, J. Power Sources, 336, 115 (2016).T. Zhang, M. Marinescu, L. O’Neill, M. Wild, and G. Offer, Phys. Chem. Chem. Phys., 17, 22581 (2015).M. Marinescu, T. Zhang, and G. J. Offer, Phys. Chem. Chem. Phys., 18, 584 (2016).D. N. Fronczek and W. G. Bessler, J. Power Sources, 244, 183 (2013).A. F. Hofmann, D. N. Fronczek, and W. G. Bessler, J. Power Sources, 259, 300 (2014).

INCIDENCE OF FUNGI IN MOMBASA GRASS SEEDS DURING THE STAGES OF THE SEED CONDITIONING PROCESS

ABSTRACT The objective of this study was to evaluate the effect of the seed conditioning process on the sanitary quality of Panicum maximum ‘Mombasa’ seeds. The seeds were sampled before processing and after exiting the seed blower and sieves (discharge from the top and bottom sieves), first gravity separator (intermediate discharge), seed treatment equipment (dyeing the seeds of the intermediate discharge from the first separator), and second gravity separator (upper, intermediate, and lower discharge). Sanitary analysis was performed by the Blotter Test method with and without surface disinfestation of the seeds, which were incubated at 20 ± 2 °C, with a photoperiod of 12 h, for 7 d. The conditioning process increased the incidence of Fusarium sp. in the Mombasa grass seeds. In addition, Cladosporium sp. and Alternaria sp. were found in and on the surface of the seeds and, therefore, can be disseminated by the seed conditioning machines. The percentage of seeds with Alternaria sp. decreased after dyeing and after the top discharge of the second gravity separator stage.

High Performance Room Temperature Sodium–Sulfur Battery by Eutectic Acceleration in Tellurium-Doped Sulfurized Polyacrylonitrile

Room temperature (RT) sodium–sulfur batteries suffer from slow reaction kinetics and polysulfide dissolution, resulting in poor performance. Sulfurized polyacrylonitrile is a unique sulfur cathode which is suggested to involve only S3–4 and shows high specific capacity. Herein, the designed Te0.04S0.96@pPAN with 4 mol % Te used as eutectic accelerator exhibits significantly enhanced reaction kinetics and excellent sulfur utilization, leading to a high performance RT Na–S battery. Te0.04S0.96@pPAN delivers capacities of 1236 and 629 mA h g–1 and 1111 and 601 mA h g–1 at 0.1 and 6 A g–1 in carbonate and ether electrolytes, respectively. Furthermore, UV–vis spectra and the shuttle current test reveal diminished sodium polysulfides in ether electrolyte, attributed to the fast kinetics enabled by Te doping. More significantly, the spectral technique and electrochemical analysis demonstrate a two-step reaction pathway in which Na2S3 and Na2S are the main intermediate and final discharge product, respectively. T...

A Quasi-Solid-State Flexible Fiber-Shaped Li-CO2 Battery with Low Overpotential and High Energy Efficiency.

The rapid development of wearable electronics requires a revolution of power accessories regarding flexibility and energy density. The Li-CO2 battery was recently proposed as a novel and promising candidate for next-generation energy-storage systems. However, the current Li-CO2 batteries usually suffer from the difficulties of poor stability, low energy efficiency, and leakage of liquid electrolyte, and few flexible Li-CO2 batteries for wearable electronics have been reported so far. Herein, a quasi-solid-state flexible fiber-shaped Li-CO2 battery with low overpotential and high energy efficiency, by employing ultrafine Mo2 C nanoparticles anchored on a carbon nanotube (CNT) cloth freestanding hybrid film as the cathode, is demonstrated. Due to the synergistic effects of the CNT substrate and Mo2 C catalyst, it achieves a low charge potential below 3.4 V, a high energy efficiency of ≈80%, and can be reversibly discharged and charged for 40 cycles. Experimental results and theoretical simulation show that the intermediate discharge product Li2 C2 O4 stabilized by Mo2 C via coordinative electrons transfer should be responsible for the reduction of overpotential. The as-fabricated quasi-solid-state flexible fiber-shaped Li-CO2 battery can also keep working normally even under various deformation conditions, giving it great potential of becoming an advanced energy accessory for wearable electronics.

The impact of wetland on neutral mine drainage from mining wastes at Luanshya in the Zambian Copperbelt in the framework of climate change.

The impact of a natural wetland ("dambo" in Zambia) on neutral mine drainage at Luanshya in the Zambian Copperbelt has been investigated during an intermediate discharge period (July) using a multi-method characterization of solid phase samples, sequential extraction analysis, X-ray diffraction, Mössbauer spectroscopy, and scanning electron microscopy combined with water analyses, isotopic analyses, and geochemical modeling. In the wetland, the principal identified solid phases in sediments were carbonates, gypsum, and ferric oxyhydroxides. A significant portion of the ochres was present as insoluble hematite. Mine drainage pH values decrease, and log [Formula: see text] values increase after inflow of water into the wetland; dissolved and suspended concentrations of Fe, Mn, Cu, and Co also decrease. Based on speciation calculations, there is no precipitation of secondary Cu and Co minerals in the period of sampling, but it can occur later in dry period when the flow rate is reduced. Concentrations of sulfate decrease, and values of δ34S(SO4) in the wetland increase in parallel, suggesting sulfate reduction is occurring. In more advanced dry period, the discharge in mine drainage stream is probably much lower and water can reach supersaturation with respect to minerals such as gypsum, which has been found in sediments. Wetlands have a positive impact on mine drainage water quality due to the removal of metals by adsorption, co-precipitation, and filtration of colloids. However, there can also be a rebound of contamination by seepage inflow downstream from the wetland. Ongoing climate change with extreme hydrologic events may enhance differences between dry and rainy seasons with resulting faster mobilization of contaminants.

A comparison of the taxonomic and trait structure of macroinvertebrate communities between the riffles and pools of montane headwater streams

Macroinvertebrate community taxonomic and trait structure showed consistent differences between riffles and pools across 12 headwater streams in the Sierra Nevada (California) even as flows varied from wet to dry years and between seasons. Densities of Ephemeroptera, Plecoptera, Trichoptera, Elmidae, Orthocladiinae and Diamesinae midges, and mites were greater in riffles, whereas Tanypodinae, Chironominae, Sialis, and Pisidium were more abundant in pools. Pools had higher densities but estimated biomass was greater in riffles. Collector-gatherer and micropredator abundances were greater in pools whereas grazers, collector-filterers, and macropredators were more abundant in riffles. Stonefly shredders were most abundant in riffles but some caddis shredders were more abundant in pools. Trait state patterns were related to food resource and physical habitat differences between riffles and pools. Of the distinct pool–riffle differences we found among taxa, only about half conformed to expectations from the literature. Pool and riffle assemblages were most dissimilar at intermediate discharge and converged at low and high flows when one or the other habitat dominated. Bioassessment sampling will need to account for these flow-related differences. Benthic invertebrate communities in these mountain streams clearly differ between pools and riffles, but the relative extent of habitats and biological similarity shift with flow regime.

Microscopic Structure and Electrolyte Nature Effects on Discharge Products of C-S Cathodes in Li-S Batteries

Intermediate and final discharge products of the lithiation of sulfur in C-S cathodes of Li-S batteries are extremely dependent on cathode morphology. When the cathode is a composite of carbon and sulfur, such morphology is in turn a function of the synthesis method. In spite of these complexities, some basic ideas can be formulated to prepare a model able to describe the C-S cathode characteristics and evolution. Here we use classical molecular dynamics with a reactive force-field to evaluate the cathode morphology and its evolution during lithiation in contact with a liquid (with or without S-containing additives) or with a solid electrolyte. The interfacial chemistry is examined with density functional theory and ab initio molecular dynamics. The same methods are used to o study the electronic conductivity of the potential insoluble products.