Performance of rectangular labyrinth weir- an experimental and numerical study

Labyrinth weirs are commonly used to increase the capacity of existing spillways and provide more efficient spillways for new dams due to their high specific discharge capacity compared to the linear weir. In the present study, experimental and numerical investigation was conducted to improve the rectangular labyrinth weir performance. In this context, four configurations were tested to evaluate the influence of the entrance shape and alveoli width on its discharge capacity. The experimental models, three models of rectangular labyrinth weir with rounded entrance and one with flat entrance, were tested in rectangular channel conditions for inlet width to outlet width ratios (a/b) equal to 0.67, 1 and 1.5. The results indicate that the rounded entrance increases the weir efficiency by up to 5%. A ratio a/b equal to 1.5 leads to an 8 and 18% increase in the discharge capacity compared to a/b ratio equal to 1 and 0.67, respectively. In addition, a numerical simulation was conducted using the opensource CFD OpenFOAM to analyze and provide more information about the flow behavior over the tested models. A comparison between the experimental and numerical discharge coefficient was performed and good agreement was found (Mean Absolute Relative Error of 4–6%).

High-capacity polymer electrodes for potassium batteries

We synthesized and investigated a series of six promising polymeric electrode materials, which incorporate multiple redox-active groups enabling high specific discharge capacity and energy density in potassium half-cells. All investigated...

Зависимость электрохимических параметров композитных SiO/C-анодов для литий-ионных аккумуляторов от состава и температуры синтеза

The results of a study of anodes obtained by carbonization of silicon monoxide by means of a reaction with solid-phase fluorocarbon CF0.8 are presented. Charge/discharge voltage profiles were studied at different currents depending on the composition and temperature of the synthesis of composites. The irreversible losses of the 1st cycle and the contribution to them of intrinsic losses due to the formation of lithium oxide and its silicates and losses associated with the formation of SEI are analyzed. A difference has been established in the behavior of anodes made of SiO carbonized by annealing with CF0.8 at T=800°C (SiO/C composite) and silicon monoxide annealed with CF0.8 at T>1000°C, at which disproportionation occurs simultaneously with the carbonization of SiO (d-SiO/C composite). The difference consisting in a higher discharge capacity, a higher Coulomb efficiency, and better rate capability of d-SiO/C is explained by a change in the composition of the SiOx matrix that occurs during the disproportionation process. The effect of the formation of d-SiO/C anodes by preliminary lithiation with a low current, after which the electrodes can be charged and discharged with much higher currents, has been discovered. The effect is explained by the amorphization of silicon crystallites and the increasing diffusion coefficient of lithium

Optimization of structural expansion and contraction for TiS2 by controlling the electrochemical window of intercalation/delithiation

The reversible layered structure of TiS2 with relaxation, such as a spring, was obtained by controlling the optimized potential range of 0.9-2.8 V (vs. Li+/Li) to yield high discharge capacity,...

Porous Fe2O3 nanorod-decorated hollow carbon nanofibers for high-rate lithium storage

Transition metal oxides (TMOs) are considered as promising anode materials for lithium-ion batteries in comparison with conventional graphite anode. However, TMO anodes suffer severe volume expansion during charge/discharge process. In this respect, a porous Fe2O3 nanorod-decorated hollow carbon nanofiber (HNF) anode is designed via a combined electrospinning and hydrothermal method followed by proper annealing. FeOOH/PAN was prepared as precursors and sacrificial templates, and porous hollow Fe2O3@carbon nanofiber (HNF-450) composite is formed at 450 °C in air. As anode materials for lithium-ion batteries, HNF-450 exhibits outstanding rate performance and cycling stability with a reversible discharge capacity of 1398 mAh g−1 after 100 cycles at a current density of 100 mA g−1. Specific capacities 1682, 1515, 1293, 987, and 687 mAh g−1 of HNF-450 are achieved at multiple current densities of 200, 300, 500, 1000, and 2000 mA g−1, respectively. When coupled with commercial LiCoO2 cathode, the full cell delivered an outstanding initial charge/discharge capacity of 614/437 mAh g−1 and stability at different current densities. The improved electrochemical performance is mainly attributed to the free space provided by the unique porous hollow structure, which effectively alleviates the volume expansion and facilitates the exposure of more active sites during the lithiation/delithiation process. Graphical abstract Porous Fe2O3 nanorod-decorated hollow carbon nanofibers exhibit outstanding rate performance and cycling stability with a high reversible discharge capacity.

Constructing zigzag-like hollow mesoporous nanospheres MoO2/C with superior lithium storage performance

Hollow mesoporous nanospheres MoO2/C are successfully constructed through metal chelating reaction between molybdenum acetylacetone and glycerol as well as the Kirkendall effect induced by diammonium hydrogen phosphate. MoO2 nanoparticles coupled by amorphous carbon are assembled to unique zigzag-like hollow mesoporous nanosphere with large specific surface area of 147.7 m2 g-1 and main pore size of 8.7 nm. The content of carbon is 9.1%. As anode material for lithium-ion batteries, the composite shows high specific capacity and excellent cycling performance. At 0.2 A g-1, average discharge capacity stabilizes at 1092 mAh g-1. At 1 A g-1 after 700 cycles, the discharge capacity still reaches 512 mAh g-1. Impressively, the composite preserves intact after 700 cycles. Even at 5 A g-1, the discharge capacity can reach 321 mAh g-1, exhibiting superior rate capability. Various kinetics analyses demonstrate that in electrochemical reaction, the proportion of the surface capacitive effect is higher, and the composite has relatively high diffusion coefficient of Li ions and fast faradic reaction kinetics. Excellent lithium storge performance is attributed to the synergistic effect of zigzag-like hollow mesoporous nanosphere and amorphous carbon, which improves reaction kinetics, structure stability and electronic conductivity of MoO2. The present work provides a new useful structure design strategy for advanced energy storage application of MoO2.

Modeling of Hierarchical Cathodes for Li-Air Batteries with Improved Discharge Capacity

The non-aqueous Li-air battery is considered to be a promising energy source for electric-vehicles owing to its ultrahigh theoretical power density. However, its commercialization is limited by the attained lower energy density value, which is mainly due to pore blockage and passivation which requires a more strategic design of the cathode. In this work, we have developed and validated a detailed one-dimensional continuum model of Li-Air battery that helps in examining the potential of hierarchical cathodes in guiding and enhancing the efficiency of ions transport and discharge product formation inside microstructures. The obtained results reveal the importance of reducing the tortuosity (shorten the path of oxygen transport) and increasing porosity at the airside of the hierarchical cathode, which improved discharge capacity at approximately 20.9 and 56%, respectively. The improved capacity is due to enhanced effective oxygen transport, impregnation of electrolyte, alignment of pores, and formation of permeable and low crystalline aggregates of Li2O2. Hence, strategies considering these insights can help in the design and fabrication of non-aqueous Li-air batteries with enhanced power density and capacity.

Synthesis of Sb2S3 NRs@rGO Composite as High-Performance Anode Material for Sodium-Ion Batteries

Sodium ion batteries (SIBs) have drawn interest as a lithium ion battery (LIB) alternative owing to their low price and low deposits. To commercialize SIBs similar to how LIBs already have been, it is necessary to develop improved anode materials that have high stability and capacity to operate over many and long cycles. This paper reports the development of homogeneous Sb2S3 nanorods (Sb2S3 NRs) on reduced graphene oxide (Sb2S3 NRs @rGO) as anode materials for SIBs. Based on this work, Sb2S3 NRs show a discharge capacity of 564.42 mAh/g at 100 mA/g current density after 100 cycles. In developing a composite with reduced graphene oxide, Sb2S3 NRs@rGO present better cycling performance with a discharge capacity of 769.05 mAh/g at the same condition. This achievement justifies the importance of developing Sb2S3 NRs and Sb2S3 NRs@rGO for SIBs.

An Identification Size of The Interdigitated Flow Field on Pressure Loss Effects and Efficiencies in Vanadium Redox Flow Battery

In vanadium redox flow battery (VRFB), the active area for charge-discharge plays an important role on the optimization of the system. In this work, the optimum flow rate and current density of Nafion 117 membranes were examined and compared using 5cm2 and 25cm2 size of interdigitated flow field to operate VRFB at maximum efficiencies and discharge capacity. During discharge, flow field 25cm2 showed the highest discharge capacity of 367.5mAh at 10mAcm-2 as compared to 5cm2 flow filed which gave 221.9mAh. For battery efficiencies, three different parameters showed significant effects on different size of interdigitated flow field. 25 cm2 size of interdigitated flow field gave higher efficiencies than 5.0 cm2 up to 98%. This research offers fundamental understandings that bigger active area is needed to fully utilize the performance of VRFB.