Overview of the Recent Progress of Suppressing the Dendritic Growth on Lithium Metal Anode for Rechargeable Batteries

The lithium metal has been considered as a competitive material for anode on the high-energy storage battery because of its various advantages, such as high capacity, low density, and the lowest electrochemical potential. However, the uncontrolled dendritic growth on the anode surface could cause the short circuit, even explosion of the battery. Therefore, strategies about how to effectively inhibit the formation of dendrites is of great importance. This paper will first give a brief introduction on the growth of dendrites. The attention is then focused on the recent advancements to suppress the dendrite growth of lithium metal, such as the optimization of electrolyte, application of artificial solid electrolyte interphase (SEI), and the modification of lithium anode. The future research directions will be presented at the end.

Stable Zinc Anodes Enabled by Zincophilic Cu Nanowire Networks

Zn-based electrochemical energy storage (EES) systems have received tremendous attention in recent years, but their zinc anodes are seriously plagued by the issues of zinc dendrite and side reactions (e.g., corrosion and hydrogen evolution). Herein, we report a novel strategy of employing zincophilic Cu nanowire networks to stabilize zinc anodes from multiple aspects. According to experimental results, COMSOL simulation and density functional theory calculations, the Cu nanowire networks covering on zinc anode surface not only homogenize the surface electric field and Zn2+ concentration field, but also inhibit side reactions through their hydrophobic feature. Meanwhile, facets and edge sites of the Cu nanowires, especially the latter ones, are revealed to be highly zincophilic to induce uniform zinc nucleation/deposition. Consequently, the Cu nanowire networks-protected zinc anodes exhibit an ultralong cycle life of over 2800 h and also can continuously operate for hundreds of hours even at very large charge/discharge currents and areal capacities (e.g., 10 mA cm−2 and 5 mAh cm−2), remarkably superior to bare zinc anodes and most of currently reported zinc anodes, thereby enabling Zn-based EES devices to possess high capacity, 16,000-cycle lifespan and rapid charge/discharge ability. This work provides new thoughts to realize long-life and high-rate zinc anodes.

Investigation of short-channel design on performance optimization effect of Hall thruster with large height-radius ratio

In this study, the neutral gas distribution and steady-state discharge under different discharge channel lengths were studied via numerical simulations. The results show that the channel with a length of 22 mm has the advantage of comprehensive discharge performance. At this time, the magnetic field intensity at the anode surface is 10% of the peak magnetic field intensity. Further analysis shows that the high-gas-density zone moves outward due to the shortening of the channel length, which optimizes the matching between the gas flow field and the magnetic field, and thus increases the ionization rate. The outward movement of the main ionization zone also reduces the ion loss on the wall surface. Thus, the propellant utilization efficiency can reach a maximum of 96.8%. Moreover, the plasma potential in the main ionization zone will decrease with the shortening of the channel. The excessively short channel will greatly reduce the voltage utilization efficiency. The thrust is reduced to a minimum of 46.1 mN. Meanwhile, because the anode surface is excessively close to the main ionization zone, the discharge reliability is also difficult to guarantee. It was proved that the performance of Hall thrusters can be optimized by shortening the discharge channel appropriately, and the specific design scheme of short channel of HEP-1350PM was defined, which serves as a reference for the optimization design of Hall thruster with large height-radius ratio. The short-channel design also helps to reduce the thruster axial dimension, further consolidating the advantages of lightweight and large thrust-to-weight ratio of the Hall thruster with large height-radius ratio.

MICROBIAL ENRICHMENT PROCESS IN THE ANODE OF MICROBIAL FUEL CELL SYSTEM USING TOFU WASTEWATER (TWW) ANAEROBIC SLUDGE

Microbial fuel cell consisting two main components which are anode and cathode materials. In the microbial fuel cell, both anode and cathode compartments are separated with a separator. Anode generates the protons and electrons while cathode converts protons into water with the presence electrons and oxygen. During the Microbial fuel cell operation, the performance of anode is very crucial due to it provides the protons and electrons. Hence, the high efficiency microbial fuel cell is very related with the high anode performance. This work addressed to the enrichment process of electroactive bacteria (EAB) in anode of microbial fuel cell. In this work, some parameters such as current generations, , and pH changes were used to assess the enrichment process of EAB was reached. In addition, the presence of EAB on the anode surface was identified based on the morphology of anode surface. The removal of COD and the pH value were determined by using the American public health analysis method and pH tester, respectively. The morphology of anode surface was analysed by using a scanning electron microscope. Whereas, current generation was tested by using a mustimeter. The removal of COD and final pH were obtained 71.4 % and 5.7, respectively. The optimum current generation was observed 0.19 mA. The surface morphology of anode before enriched with microbes was clear surface, while after enriched with microbes was attached by microbes. The removal of COD, pH changes, current generation and morphology of anode surface could be used to assess the EAB in the anode compartment. Keywords: Microbial fuel cell; anode; cathode; electroactive bacteria; pH changes.

The Effect of Brush Plate Structure and Operating Parameters on the Energy Consumption of Electrolytic Cells

The nickel powder brush plate is a core component of the direct contact between the cleaning machine and cathode plate of an electrolyzer, and its movement in the electrolytic cell will affect the energy consumption of the electrolyzer. In order to optimize the structure of the brush plate, a cleaning trolley brush plate was taken as the research object, a mathematical model of its electrolyzer was established, and the reliability was subsequently verified. The influence of the structural and operating parameters of the brush plate on the energy consumption of the electrolytic cell was studied. The research results show that additional energy consumption is the lowest in the process of cleaning a return grooved brush plate. Brush plates with a large slotting area have less impact on the energy consumption of the electrolyzer. The slotting method, where the anodes are arranged directly opposite each other and relatively concentrated, can be adapted to render a more uniform current density distribution on the anode surface, with lower energy consumption and less variation in voltage and current. With the increasing number of slots from one to three, the current density distribution on the anode surface became more uniform, with a reduction in the variation range of the slot voltage and current in the branch where the cathode plate was cleaned and a decreased energy consumption. With the linear increase in brush cleaning speed, the impact time of the brush plate on the electrolyzer decreased nonlinearly, and as the extent of this decrease gradually diminished, the additional energy consumption showed the same trend. These research results were then used as a basis for optimizing the existing commonly used empirical C-brush plates. Following optimization, the current density distribution on the anode surface was found to be more uniform, the variation amplitude of tank voltage was reduced by 34%, the current drop amplitude of the branch circuit where the brushed cathode plate was located was reduced by 39%, the impact time on the current field of the electrolytic tank was reduced by 40%, and the additional energy consumption was reduced by 50.9%. These results can be served as a reference for further theoretical research related to brush plates.

A novel fragmented anode biofilm microbial fuel cell (FAB–MFC) integrated system for domestic wastewater treatment and bioelectricity generation

Background The critical MFC design challenge is to increase anode surface area. A novel FAB–MFC integrated system was developed and evaluated for domestic wastewater treatment. It was operated in fed-batch flow mode at 1–3 days of HRT with 755 mg/L CODIN and 0.76 kg-COD/m3/day. The study includes anaerobic-MFC and aerobic-MFC integrated systems. Microbial electrode jacket dish (MEJ-dish) with hybrid dimension (HD) was invented, first time to authors’ knowledge, to boost anode biofilm growth. The treatment system with MEJ+ (FAB) and MEJ− (MFC) anode are called FAB–MFC and MFC, respectively. Results Fragmented variable anode biofilm thickness was observed in FAB than MFC. The FAB–MFC (FAB+) simple technique increases the anode biofilm thickness by ~ 5 times MFC. Due to HD the anode biofilm was fragmented in FAB+ system than MFC. At the end of each treatment cycle, voltage drops. All FAB+ integrated systems reduced voltage drop relative to MFC. FAB reduces voltage drops better than MFC in anaerobic-MFC from 6 to 20 mV and aerobic-MFC from 35–47 mV at 1 kΩ external load. The highest power density was achieved by FAB in anaerobic-MFC (FAB = 104 mW/m2, MFC = 98 mW/m2) and aerobic-MFC integrated system (FAB = 59 mW/m2, MFC = 42 mW/m2). Conclusions The ∆COD and CE between FAB and MFC could not be concluded because both setups were inserted in the same reactor. The integrated system COD removal (78–97%) was higher than the solitary MFC treatment (68–78%). This study findings support the FAB+ integrated system could be applied for real applications and improve performance. However, it might depend on influent COD, the microbial nature, and ∆COD in FAB+ and MFC, which requires further study. Graphic abstract

Iron Oxide–Modified Carbon Electrode and Sulfate-Reducing Bacteria for Simultaneous Enhanced Electricity Generation and Tannery Wastewater Treatment

The microbial fuel cell (MFC) is emerging as a potential technology for extracting energy from wastes/wastewater while they are treated. The major hindrance in MFC commercialization is lower power generation due to the sluggish transfer of electrons from the biocatalyst (bacteria) to the anode surface and inefficient microbial consortia for treating real complex wastewater. To overcome these concerns, a traditional carbon felt (CF) electrode modification was carried out by iron oxide (Fe3O4) nanoparticles via facile dip-and-dry methods, and mixed sulfate-reducing bacteria (SRBs) were utilized as efficient microbial consortia. In the modified CF electrode with SRBs, a considerable improvement in the bioelectrochemical operation was observed, where the power density (309 ± 13 mW/m2) was 1.86 times higher than bare CF with SRBs (166 ± 11 mW/m2), suggesting better bioelectrochemical performance of an SRB-enriched Fe3O4@CF anode in the MFC. This superior activity can be assigned to the lower charge transfer resistance, higher conductance, and increased number of catalytic sites of the Fe3O4@CF electrode. The SRB-enriched Fe3O4@CF anode also assists in enhancing MFC performance in terms of COD removal (>75%), indicating efficient biodegradability of tannery wastewater and a higher electron transfer rate from SRBs to the conductive anode. These findings demonstrate that a combination of the favorable properties of nanocomposites such as Fe3O4@CF anodes and efficient microbes for treating complex wastes can encourage new directions for renewable energy–related applications.

Numerical simulation of low-current vacuum arc jet considering anode evaporation in different axial magnetic fields

As the main source of the vacuum arc plasma, cathode spots (CSs) play an important role on the behaviors of the vacuum arc. Their characteristics are affected by many factors, especially by the magnetic field. In this paper, the characteristics of the plasma jet from a single CS in vacuum arc under external axial magnetic field (AMF) are studied. A multi-species magneto-hydro-dynamic (MHD) model is established to describe the vacuum arc. The anode temperature is calculated by the anode activity model based on the energy flux obtained from the MHD model. The simulation results indicate that the external AMF has a significant effect on the characteristic of the plasma jet. When the external AMF is high enough, a bright spot appears on the anode surface. This is because with a higher AMF, the contraction of the diffused arc becomes more obvious, leading to a higher energy flux to the anode and thus a higher anode temperature. Then more secondary plasma can be generated near the anode, and the brightness of the ‘anode spot’ increases. During this process, the arc appearance gradually changes from a cone to a dumbbell shape. The appearance of the plasma jet calculated in the model is consistent with the experimental results.