Cycling Efficiency Research Articles

Planktonic carbon metabolism of an underwater coral atoll in the oligotrophic sea: a case study of Zhongsha Atoll, Central South China Sea

Coral atolls are widely recognized as oases of remarkable biodiversity and productivity within the oligotrophic open ocean. However, considerable debate surrounds the net carbon metabolism of planktonic communities in oceanic coral atolls and their contribution to the overall carbon budget of the ocean. Zhongsha Atoll, situated in the central South China Sea, represents one of the largest submerged reef atolls globally. Despite its significance, the ecological environment and characteristics of community production and metabolism at Zhongsha Atoll have been scarcely studied, and it remains uncertain whether these features differ from those observed in barrier-type reefs. In this study, we examined the gross primary production (GPP), community respiration (CR), and net community production (NCP) of the planktonic community in Zhongsha Atoll and its surrounding waters from 22 June to 6 July 2020. We also analyzed the potential influences of their distribution patterns. Our findings revealed that CR did not vary significantly with depth and it was considerably higher than GPP. As a result, the waters at the euphotic depth of Zhongsha Atoll were found to be heterotrophic, with negative NCP. Additionally, the correlation analysis demonstrated a negative relationship between NCP and CR. The NCP values were -35.28 ± 26.73 and -53.18 ± 31.77 mg C m-3 d-1 for the surface and chlorophyll maximum (DCM) layers, respectively. The NCP for the upper water column was -3023 mg C m-2 d-1. The waters above the reef flat (FL) exhibited higher primary productivity, with GPP in the surface and DCM layer being 1.61 and 2.71 times greater, respectively, than in the surrounding oceanic regions. However, the FL displayed a greater level of heterotrophy due to its stronger CR. In conclusion, the carbon metabolism of the planktonic community in submerged Zhongsha Atoll acts as a source of atmospheric CO2, and the distribution of coral reefs considerably contributes to the efficiency of carbon cycling within the atoll.

Cover crops impact phosphorus cycling and environmental efficiency in a corn–soybean system

AbstractSolutions to simultaneously meet crop phosphorus (P) demand and reduce P loss from agricultural systems are required to improve the sustainability of our production. Our objective was to determine the effect of cover crop addition (with cover crop [CC], and without cover crop [NC]) and P fertilizer management (zero P control [CN], fall broadcast [FB], and spring injected [SI]) on P cycling, agronomic P use efficiency (PUE), and environmental P use efficiency (EPUE), measured as the percent of P lost in runoff water, in a no‐till corn (Zea mays)–soybean [Glycine max (L.) Merr.] rotation. The experiment was a 2 × 3 factorial. Both FB and SI increased P cycling through the main crop and cover crop tissue, compared to the CN. Cover crop did not affect main crop P uptake, removal in grain, or return to soil in crop residue, but CC treatment increased total P uptake and return in the system. Cover crop effects on P uptake, removal, and return were the same regardless of P fertilization treatments. Phosphorus fertilizer and CC treatments did not affect PUE. Both FB and SI P fertilizer management decreased EPUE, although SI tended to decrease EPUE less than FB. Cover crop significantly improved EPUE only in 2019, when CC reduced erosion losses. Therefore, cover crops were not consistently beneficial for reducing the environmental effects of P fertilization, and their use cannot replace the importance of sound P fertilizer stewardship, including sub‐surface P placement. However, cover crops play an important role in improving EPUE in years with high erosion loss potential.

Promoting the Cation Utilization in Energy‐Dense Sodium Metal Battery Prototypes: Strategies, Analysis, and Prospects

Sodium metal batteries (SMBs) have garnered significant attention among the most promising energy storage devices due to their high theoretical energy densities and availability of charge carrier sources. However, the large volume expansion of the hostless anode and Na dendrite protrusion destabilize the solid–electrolyte interphase (SEI), meanwhile the irreversible depletion of Na+ ions would compromise the coulombic efficiency and lead to the unsatisfactory cation utilization during the repetitive cycling. Hitherto, a series of optimization strategies are proposed to promote SMB cation utilization, including homogenizing the cation influx toward the metallic substrate, regulating the composition of the SEI layer, and suppressing the volume propagation of metallic deposition. Most of these methods, however, are still based on empirical attempts and lack the systematic study to elucidate the interplay between the structural evolution of the electrodes and the cation utilization degree on the device level. Therefore, this review aims to consolidate the understanding of critical factors that promote the cycling efficiency and their correlations through the performance assessment on the device level. By leveraging operando characterization techniques, the future studies seek to emphasize the pivotal characteristics at multiple scales that contribute to the enhanced cation utilization degree.

Tribological devices in cycling: A review

This review, focussed on transmission efficiency and wear in cycling, presents existing friction measuring devices. It discusses their pros and cons and compares the lubrication regime they are in to the ones determined for elite cycling. Finally, it addresses technical guidelines for measuring friction forces from the transmission ( Ft). Ft depend on normal load and coefficient of friction (µ). Indeed, these factors are influenced by chain tension, alignment and velocity, sprocket size, lubricants and contamination. Such parameters also have an impact on lubrication regime which influences µ. To characterise Ft, measuring devices were developed. Forty devices were classified in five categories, ranging from those closest to ecological conditions to the most specific ones. Full transmission (FTR) and single speed rigs (SSR) results can be extrapolated into real cycling, although they are less accurate as they involve more elements. Dedicated rigs engender high precision measurements on precise phenomena. All lubrication regimes are encountered in elite cycling, which is in good accordance with most of the testing conditions presented in this review, especially FTR and SSR. If Boundary and Mixed regimes are unavoidable due to the reciprocating movements of the chain elements, they should be limited. The Elasto-Hydrodynamic regime is on target as it provides low µ and wear. In conclusion, the closer the measure is to real cycling, the higher the variability. Inversely, dedicated rigs are accurate but less representative of complete transmissions. Technology improvements now make FTR and SSR reliable enough to measure small differences, along with a strong protocol.

Diffusion and Creep in Lithium Metal Anodes Induced by Plating and Stripping Reactions

Electrodeposition of lithium on lithium metal negative electrodes (anodes) of liquid cells produces filamentary deposits, resulting in poor cycling efficiency. Experiments suggest that filaments grow by extrusion of metal from the substrate, due to compressive stress introduced during deposition. A model is presented that explores the origin of stress generated in the anode during plating-stripping cycles. According to the model, plating or stripping reactions insert or remove lithium atoms at the interface between the metal and the solid electrolyte interphase (SEI) layer. Stress is induced by the resulting diffusion processes, with diffusion-induced strain accommodated by inelastic creep. Stress distributions during cycling are calculated, and are used in turn to predict curvature transients that would be measured in beam-deflection experiments. The calculations account for the three-dimensional surface morphology, since surface features that protrude above the surface plane do not contribute to curvature changes. Comparisons with recent curvature measurements demonstrate detailed agreement, with diffusion and creep parameters close to literature values. The results support the hypothesis that electrochemical reactions intrinsically generate stress. The model can serve as a framework for analysis of morphogical instability of the lithium anode interface in both liquid and solid-state cells.

High dielectric filler for all-solid-state lithium metal battery

Lithium metal with its high theoretical capacity and low negative potential is considered one of the most important candidates to raise the energy density of all-solid-state batteries. However, lithium filament growth and its induced solid electrolyte decomposition pose severe challenges to realize a long cycle life. Here, dendrite growth in solid-state Li metal batteries is alleviated by introducing a high dielectric material, barium titanate, as a filler that removes the electric field gradients that catalyze dendrite formation. In symmetrical Li-metal cells, this results in a very small over-potential of only 48 mV at a relatively high current density of 1 mA cm−2, when cycling a capacity of 2 mA h cm−2 during 1700 h. The high dielectric filler improves the Coulombic efficiency and cycle life of full cells and suppresses electrolyte decomposition as indicated by solid-state nuclear magnetic resonance (NMR) and X-ray photoelectron spectroscopy (XPS) measurements. This indicates that the high dielectric filler can suppress dendrite formation, thereby reducing solid electrolyte decomposition reactions, resulting in the observed low overpotentials and improved cycling efficiency.

Differences between cation and anion storage electrochemistry of graphite and its impact on dual graphite battery

The redox-amphoteric nature of graphite is tactically utilized to store cations and anions simultaneously in a dual graphite battery (DGB). The major differences between cation and anion storage electrochemistry of graphite are identified here and their impacts on the electrochemical performances of DGBs are analyzed. All the differences are found to originate primarily from ionic size mismatch (76 p.m. of Li+vs. 254 p.m. of PF6−) that further induces kinetic and thermodynamic limitations upon intercalation. The electrochemical studies reveal that the anion intercalation lags behind the cation because of a higher energy barrier for the interconversion among (PF6)Cx stages, the occurrence of a valley-type region in the discharge profile that delays deintercalation by 500 mV, dynamic changes in organic-rich cathode electrolyte interphase, and sluggish diffusion inside graphite bulk. In contrast, cation intercalation affects DGBs' performance negatively due to higher desolvation barriers and lithium plating on the anode surface at higher current densities. Therefore, the cathode limits the capacity and cycling efficiency, whereas the anode restricts cycle life and power density. This work also explores the strategies to mitigate the degradation pathways by electrolyte modification.

Composite super-capacitor/Na-ion battery with self-healing Fe–Cr alloy electrodes

In this study, we synthesize a novel self-healing supercapacitor (SC) by combining a thermally and alkali-activated carbon interface with a unique chromium–iron alloy. Detailed device electrochemistry is presented, complemented by characterizations through XRD, SEM, and EDS analyses of electrode surfaces. We introduce rapid cyclic voltammetric measurements to illuminate electrical performance and charge storage of fabricated SCs. SEM measurements demonstrate heightened cycling efficiency, indicating reduced electrolyte degradation and dormant sodium metal formation. XRD measurements support SCs’ self-enhancement, evidenced by sodium metal formation and improved crystalline properties on electrode surfaces. SEM micrographs reveal distinct nanostructures—nanoneedles, nanoflowers, carbon nanotubes, and graphene—formed during charge–discharge cycles. EDS confirms reversible Na metal formation, while increased Cr peaks, acting as corrosion inhibitors, highlight self-healing, extending SC lifespan. Attaining a capacitance of around 30 mF and capacity of 55.6 mWh/kg, the material offers at least 1500 μF/g. Initial results showcase a composite SC/Na-ion battery with favorable and scalable SC characteristics.

Laser‐Induced Carbon Nanofiber‐Based Redox Cycling System

AbstractRedox cycling is a powerful amplification strategy for reversible redox species within miniaturized electrochemical sensors. Herein, we generate three‐dimensional (3D) porous carbon nanofiber electrodes by CO2 laser‐writing on electrospun polyimide (PI) nanofiber mats, referred to as laser‐induced carbon nanofibers (LCNFs). The technique allowed the fabrication of interdigitated electrode (IDE) arrays with finger width and gap distance of ~400 μm and ~40 μm, respectively, offering approximately 3.5 times amplification efficiency (AF) and 95 % collection efficiency (CE). Such dimensions could not be achieved with IDEs fabricated on conventional PI film because the devices were short‐circuited. Stacked electrodes were also constructed as an alternative to the IDE design. Here, nanofiber mats as thin as ~20 μm were fabricated and used as vertical insulation between two LCNF band electrodes. While redox cycling efficiency was similar, the IDE design is more favorable considering the lower complexity and better signal reproducibility. Our strategy thus paves the way for creating flexible 3D porous electrodes with redox cycling ability that can be integrated into microfluidics and lab‐on‐a‐chip systems. In particular, the devices offer inherent flow‐through features in miniaturized analytical devices where separation and sensitive detection could be further realized.

Herbicides versus Nitrogen Cycle: Assessing the Trade-Offs for Soil Integrity and Crop Yield—An In-Depth Systematic Review

The interaction of herbicides in the nitrogen cycle and their consequences on soil health and agricultural production are essential topics in agronomic research. In this systematic review article, we have synthesized recent studies on this subject. The results revealed that the indiscriminate use of herbicides can have negative effects on vital processes in the nitrogen cycle, such as reduced enzymatic activity and microbial respiration. Moreover, herbicides alter the soil microbial composition, affecting nitrogen cycling-related activities. Symbiotic nitrogen fixation is also impaired, resulting in a reduction in the population of nitrogen-fixing bacteria and a decrease in the availability of this nutrient in the soil. These effects compromise soil fertility and the release of nitrogen to plants. Therefore, sustainable agricultural practices must be adopted, considering nitrogen cycling efficiency and the preservation of soil and natural resources. This understanding is crucial for guiding appropriate management strategies aimed at minimizing the negative effects of herbicides on the nitrogen cycle and ensuring soil health and agricultural productivity.

Effects Of Low-volume High-intensity Training With Blood Flow Restriction On Sub-maximal Cycling Efficiency

Effects Of Low-volume High-intensity Training With Blood Flow Restriction On Sub-maximal Cycling Efficiency

Germanium–Cobalt–Indium Nanostructures as Anodes of Lithium-Ion Batteries for Room- and Low-Temperature Performance

Germanium–cobalt–indium nanostructures were synthesized via cathodic electrodeposition from aqueous complex solutions of Ge (IV) and Co (II) with drop-like indium crystallization centers. This approach features simplicity, avoids heating and allows using cheaper GeO2 instead of pure Ge as starting material. Further, in this case, target nanostructures grow directly upon the substrate. Various analytical methods (scanning electron microscopy, transmission electron microscope and X-ray diffraction) were used for characterization of the nanostructures under study. The samples obtained consist of an array of globular particles of 200 to 800 nm, with nanowires in between. The globules, in turn, contain primary particles of 5 to 10 nm consisting of cobalt, germanium and oxygen. Nanowires consist of germanium and indium. The electrochemical properties of the above-mentioned nanostructures were assessed with cyclic voltammetry and galvanostatic cycling. The germanium–cobalt–indium nanostructures are characterized by a high specific capacity upon lithium insertion, which is approximately 1350 mAh/g at C/8, and a high Coulomb cycling efficiency in the first cycle (approximately 0.76). Germanium–cobalt–indium nanostructures show the ability to operate at high rates up to 16 C at a wide temperature range from +20 to −35 °C.

Cycling Efficiency Improvement of Solid-State Batteries-Laser Textured Interfaces

Solid-state lithium metal batteries (SS-LMBs) with ceramic electrolytes have attracted significant interest towards their potential to produce safe and powerful storage devices. Among ceramic electrolyte materials utilized in SS-LMBs, non-flammable perovskites (La2/3-xLi3xTiO3, LLTO) are cost-effective and have a wider electrochemical window than conventional liquid electrolytes (> 5V). However, the high interfacial resistance at the LLTO/cathode interface restricts the reversible capacity and the cycling efficiency of SSLMBs. Herein, a novel approach of laser texturing at the interface was investigated as a solution to these two challenges.In this study, the laser-texturing technique was first used to produce micro-patterns on the side of the LLTO against the cathode. This increased surface contact area provided more pathways for Li-ion migration at the interface, leading to decreased interfacial resistance and an improved battery energy density. A few drops of liquid electrolyte were added to fill the void spaces between the laser-textured LLTO and the cathode.Overall, this study conceptually proved the effectiveness of using laser texturing to improve the interfacial contact. Further efforts are needed to optimize the pattern design and establish a more stable interface that could enable long-term cycling of the SS-LMBs.

(Invited) High-Performance Lithium Metal Batteries

The success of rechargeable lithium-ion batteries (LIBs) has brought evident convenience to human society, but state-of-the-art LIBs with a carbon anode are approaching their energy density limits. Li metal is considered the ultimate anode material due to its ultra-high theoretical specific capacity of 3860 mAh g-1, which is more than 10 times higher than lithiated graphite. Nonetheless, Li anode suffers from poor safety and low cycling efficiency due to its high reactivity. Electrolytes that work with Li anode should possess excellent stability against Li metal or form a highly passivating interface. It is also critical to control the amount of Li in the cell, preferably having no excess Li at the anode side.1 In this presentation, next-generation electrolytes that enable such types of high-performance Li metal batteries will be discussed, including advanced liquid electrolytes,2 garnet-type ceramic electrolytes3–5 and hybrid electrolytes.6,7 References C. Zhou, A. J. Samson, M. A. Garakani, and V. Thangadurai, J. Electrochem. Soc., 168, 060532 (2021).C. Zhou et al., Energy Storage Mater., 42, 295–306 (2021) https://doi.org/10.1016/j.ensm.2021.07.043.S. P. Kammampata, R. H. Basappa, T. Ito, H. Yamada, and V. Thangadurai, ACS Appl. Energy Mater., 2, 1765–1773 (2019).S. P. Kammampata, H. Yamada, T. Ito, R. Paul, and V. Thangadurai, J. Mater. Chem. A, 8, 2581–2590 (2020).C. Zhou, A. J. Samson, K. Hofstetter, and V. Thangadurai, Sustain. Energy Fuels, 2, 2165–2170 (2018).S. Bag, C. Zhou, P. J. Kim, V. G. Pol, and V. Thangadurai, Energy Storage Mater., 24, 198–207 (2019) https://doi.org/10.1016/j.ensm.2019.08.019.C. Zhou, S. Bag, T. He, B. Lv, and V. Thangadurai, Appl. Mater. Today, 19, 100585 (2020) https://doi.org/10.1016/j.apmt.2020.100585.

Performance and economic analysis of steam extraction for energy storage to molten salt with coupled ejector and thermal power units

A new thermal power unit peaking system coupled with thermal energy storage and steam ejector was proposed, which is proved to be technically and economically feasible based on the simulation of a 600 MW thermal power unit. Results show that the percentage of exergy losses in the retrofitted system is in the order of condenser, turbine and thermal energy storage system, with the exergy losses in the heat release process accounting for approximately 70 % of the cycle. The condenser and evaporator corresponding to the storage and heat processes account for 60 % of the total exergy losses in thermal energy storage system. The retrofitted system has a maximum cycle efficiency of 70–80 % with low and peak modulation rates of 16.5 % and 11.7 %. Extraction of main steam dominates the peaking rate and cycling efficiency compared to extraction of reheat steam. Increasing the main steam pressure at the ejector inlet increases the low peaking rates by 1.5 %, while reducing the molten salt flow rate per unit peaking depth by 10 t/h, which is essential for the stable operation of the retrofitted system. The economic analysis of the retrofitted system shows that the system operating time is the main factor affecting the payback period compared to the interest rate and starts to be profitable in 3.8 years, with later profitability of up to RMB 25 million/year. Further analysis reveals that two different extractions of reheat steam with the same extraction of main steam will achieve the same payback period, which offers a variety of possibilities for practical operational scenarios. In addition, when the extraction of main steam is <250 t/h, the payback time of the system will exceed 15 years, at which point it will be challenging to meet the economic viability of the retrofitted system.

Biomechanical Analysis of Recreational Cycling with Unilateral Transtibial Prostheses

Leg prostheses specially adapted for cycling in patients with transtibial amputation can be advantageous for recreational practice; however, their required features are not fully understood. Therefore, we aimed to evaluate the efficiency of unilateral cycling with a transtibial prosthesis and the characteristics of different attachment positions (middle and tip of the foot) between the prosthetic foot and the pedal. The cycling practice was performed on an ergometer at 40 W and 60 W resistance levels while participants (n = 8) wore custom-made orthoses to simulate prosthesis conditions. Using surface electromyogram, motion tracking, and power meter pedals, biomechanical data were evaluated and compared with data obtained through regular cycling. The results showed that power delivery became more asymmetrical at lower workloads for both orthosis conditions, while hip flexion and muscle activity of the knee extensor muscles in the sound leg increased. While both pedal attachment positions showed altered hip and knee joint angles for the leg wearing the orthosis, the middle of the foot attachment presented more symmetric power delivery. In conclusion, the middle of the foot attachment position presented better symmetry between the intact and amputated limbs during cycling performed for rehabilitation or recreation.

Drought re-routes soil microbial carbon metabolism towards emission of volatile metabolites in an artificial tropical rainforest

Drought impacts on microbial activity can alter soil carbon fate and lead to the loss of stored carbon to the atmosphere as CO2 and volatile organic compounds (VOCs). Here we examined drought impacts on carbon allocation by soil microbes in the Biosphere 2 artificial tropical rainforest by tracking 13C from position-specific 13C-pyruvate into CO2 and VOCs in parallel with multi-omics. During drought, efflux of 13C-enriched acetate, acetone and C4H6O2 (diacetyl) increased. These changes represent increased production and buildup of intermediate metabolites driven by decreased carbon cycling efficiency. Simultaneously,13C-CO2 efflux decreased, driven by a decrease in microbial activity. However, the microbial carbon allocation to energy gain relative to biosynthesis was unchanged, signifying maintained energy demand for biosynthesis of VOCs and other drought-stress-induced pathways. Overall, while carbon loss to the atmosphere via CO2 decreased during drought, carbon loss via efflux of VOCs increased, indicating microbially induced shifts in soil carbon fate.

Simulation of urban non-motorized traffic: A agent-based modeling approach based on big data of bike sharing and social force model

Encouraging cycling, one of the urban non-motorized transport modes, has been well recognized as an environment-friendly way that alleviates urban traffic congestions and solves the first/last mile issue. However, concerns about the efficiency and safety of urban cycling have been widely made by urban planners due to the unclear right-of-way and discontinuous non-motorized corridor for cycling. This study uses the dynamic location data of the Meituan Bike (formerly Mobike) in the Hi-tech Park area of Shenzhen to analyze the spatial-temporal variations of bikeshare use, aiming at identifying the traffic corridors of cycling. Combined with agent-based modeling technique and social force model, this research proposes a new approach of simulating the urban non-motorized traffic, and hence provides valuable insights for building bicycle lanes for cycling corridors. The results show that (1) the usage of bike sharing during weekdays is 2.5 times that on weekdays, and the cycling corridors are usually the main and secondary roads that are in the vicinity of the metro stations; (2) adding bicycle lanes can reduce the traffic density of the non-motorized volume by 6% in an overall, and save the travel time of cyclists and pedestrians by 6.4% and 3.7%, respectively.

Regulation of the pore structure of carbon nanosheets based electrocatalyst for efficient polysulfides phase conversions

The practical applications of lithium-sulfur (Li-S) batteries are hampered by the sluggish redox kinetics and polysulfides shuttle in the cyclic process, which leads to a series of problems including the loss of active materials and poor cycling efficiency. In this paper, the pore structures of carbon nanosheets based electrocatalysts were precisely controlled by regulating the content of water-soluble KCl template. The relationship between pore structures and Li-S electrochemical behavior was studied, which demonstrates a key influence of pore structure in polysulfides phase conversions. In the liquid-sloid redox reaction of polysulfides, the micropores and small mesopores (d < 20 nm) exhibited little impact, while the mesopores (d > 20 nm) and macropores played a decisive role. As a typical exhibition, the nickel-embedded carbon nanosheets (Ni-CNS) with a high content of large mesopores and macropores can aid Li-S batteries in exhibiting stable cycling performance (760.1 mAh g−1 at 1 C after 300 cycles) and superior rate capacity (847.8 mAh g−1 at 2 C). Furthermore, even with high sulfur loading (8 mg cm−2) and low electrolyte (E/S is around 6 µL mg−1), the high area capacity of 7.7 mAh cm−2 at 0.05 C could be achieved. This work can provide a guideline for the design of the pore structure of carbon-based electrocatalysts toward high-efficiency sulfur species redox reactions, and afford a general, controllable, and simple approach to constructing high performance Li-S batteries.

Characterizing the Impact of Oligomerization on Redox Flow Cell Performance

AbstractRedox flow batteries (RFBs) are hindered by complex failure modes, particularly crossover through the membrane, resulting in capacity fade and reduced cycling efficiencies. Redox‐active oligomers (RAOs) have recently been proposed for mitigating this phenomenon while maintaining sufficient transport properties; however, to date, few studies have quantified how the chemical and electrochemical properties of RAOs influence their performance in redox flow cells. Here, we demonstrate that oligomeric derivatives of 2,2,6,6‐tetramethylpiperidine 1‐oxyl (TEMPO) exhibit lower diffusivities than the monomeric species but retain facile charge transfer characteristics. The size‐dependent variations in mass transport rates directly translate to differences in flow cell polarization and symmetric cycling performance. Post‐mortem analyses reveal that oligomerization does not meaningfully alter decay processes as evinced by similar capacity fade across all species. Broadly, these findings corroborate and extend upon previously developed relationships between molecular size, electrochemical properties, and flow cell performance.