Uneven Electric Field Research Articles

Bi-Functional Agarose-Filled Porous Polysulfone Protective Layer for Dendrite-Free Zn Anode.

The uneven electric field and slow Zn2+ desolvation lead to rapid dendrite growth during Zn plating and stripping, which severely deteriorates the performance of Zn metal anodes (ZMAs) in Zn-ion batteries (ZIBs). Although polymer-based artificial protective (PBAP) layers are widely applied to homogenize the electric field of ZMAs, they often fail to promote the desolvation process that eventually induces Zn dendrite growth. Herein, a bi-functional protective layer, comprising a finger-like porous matrix of polysulfone (PSF) and a hydroxyl-rich filler of agarose (AG), is constructed to suppress Zn dendrite growth. COMSOL simulation demonstrates the ZMAs with bi-functional protective layers (Zn@PSF/AG) exhibit uniform electric field and Zn2+ distribution. Besides, the Zn@PSF/AG has both low desolvation energy and nucleation overpotential, effectively promoting the desolvation of Zn2+. Therefore, the Zn@PSF/AG symmetric cell exhibits excellent cycling performance, achieving 4200h at 1mA cm-2/1 mAh cm-2 and 1000h at 5mA cm-2/5 mAh cm-2. When coupling with ZnxV2O5 (ZnVO) cathode, the ZnVO‖Zn@PSF/AG full cell shows similarly high cycling stability, maintaining 72% of its capacity after 7000 cycles at 10 A g-1. This research highlights the positive roles of PBAP layer with multi-functional matrix-filler structure in developing long-life ZIBs.

A data-driven model for the field emission from broad-area electrodes

Electron emission from cathodes in high field gradients is a quantum tunneling effect. The 1928 Fowler–Nordheim field emission (FE) equation and the 1956 Murphy–Good FE equation have traditionally been key in describing cold field emissions, offering estimates for emitters for almost a century. Nevertheless, applying FE theory in practice is often constrained by the lack of data on the distribution and geometry of the emission sites. Predictions become more challenging with an uneven electric field distribution at the cathode surface. Consequently, FE formulations are frequently calibrated using current–voltage data after test, limiting their efficacy as true predictive models.This study develops an alternative model for field emission using a data-driven predictive approach based on (1) vast experimental data, (2) electrostatic simulations of the cathode surface, and (3) detailed material and geometry properties, which together overcome these limitations. The objective of this work is to develop and harness this comprehensive dataset to train a machine learning model capable of providing precise predictions of the cathode current in order to further the understanding and application of field emission phenomena. More than 259 h of experimental data have been processed to train and benchmark some of the well-known machine learning models. After two stages of optimization, a coefficient of determination >98% is achieved in the prediction total field emission current using ensemble models.

3D self-supporting core-shell silicon-carbon nanofibers-based host enables confined Li+ deposition for lithium metal battery

Three-dimensional (3D) porous hosts play pivotal roles in realizing dendrite-free lithium metal anodes (LMAs) owing to their high specific area. However, uneven local electric field and lack of lithiophilic sites on the reactive interface cause nonuniform lithium ion (Li+) deposition, leading to Li dendrite growth and parasitic reactions. These issues will inevitably incur short cycling life and severe safety hazards of lithium metal batteries. Herein, a 3D self-supporting host composed of hollow carbon nanofibers incorporated with silicon (Si) nanoparticles inside (Si-HCF) is constructed as Li metal host by a scalable coaxial electrospinning technique. During the first cycle, the Si nanoparticles is alloyed with Li+ to form lithiophilic Li-Si alloy, contributing to deliver a low nucleation overpotential and homogeneous surface potential confirmed by Kelvin probe force microscopy, finally guiding Li+ flux homogeneously throughout the fibrous mat. As expected, the Li metal can percolate through Si-HCF host reversibly without uncontrollable Li dendrites and the Si-HCF exhibits a stable cycle life of Li plating/stripping over 1400 h. Additionally, the full cell combined with LiFePO4 cathodes presents steady cycling over 400 cycles with a high average coulombic efficiency of 99.4 %. This work provides new insights for the synthesis of 3D hosts with controllable nucleation sites to homogenize Li+ deposition in LMAs.

3D structured lithiophilic current collector with lithiation nucleation overpotential near 0 V for dendrite-free lithium metal anode

The poor lithium affinity of most metal skeletons leads to uneven electric field distribution, resulting in the notorious Li dendrite growth. Herein, a 3D structured Cu mesh@Ag current collector is introduced using a simple chemical plating method to enable dendrite-free Li anode. The high electronic conductivity and matrix pore structure of Cu mesh can alleviate the local current density and provide buffer space for lithium deposition. The lithiophilic Ag can form infinite solid solution with Li while reducing the initial lithiation nucleation overpotential to about 0 V, achieving homogenous Li deposition. As a result, the symmetric cell can maintain a low polarization voltage (20 mV) after cycling at 0.5 mA cm-2 for 1300 h Full cells assembled with LiFePO4 cathode present a long-term cycling stability of 500 cycles at 1C with a capacity retention of 80.3%. This work provides a reliable approach to create stable Li-metal batteries.

Li-Sn Alloyed Layer Containing Artificial SEI on Li-Metal Anode for Superior Lithium Metal Batteries: Development and Understanding of Anode/Electrolyte Interfacial Phenomena

Modern civilization and cutting-edge technologies and tools are highly dependent on energy storage devices and demand efficient and long-lasting high-energy-density storage devices. Lithium metal batteries have surpassed their competitors concerning energy density due to their inherent high specific capacity (3860 mAh/g) and the lowest electrochemical potential (-3.04 V vs. standard hydrogen electrode), proving to be one of the most favorable energy storage devices for smart and mobile gadgets, electric automobiles, grid storage, etc. However, safety-threatening and performance-decay challenges associated with lithium metal anodes, such as lithium dendrite formation, uncontrolled parasitic reactions between Li-metal and electrolyte, low coulombic efficiency, dead Li-formation, etc., restrict its employment in practical batteries. The root cause of the dendrite formation is poor Li-ion conductivity of bulk lithium metal, which results in an uneven electric field distribution, leading to non-uniform Li deposition/stripping upon repeated charge/discharge. Herein, a facile chemical reduction process is being opted to fabricate a highly Li-ion diffusive Li-Sn-based artificial SEI layer on the lithium metal surface to prevail over the above-mentioned issues. Therefore, upon careful concentration investigation of reactants, 25 mM precursor concentration (SnCl4 in EC: DMC in 1:1 volume ration) demonstrated the best electrochemical performance, revealing a cumulative capacity of over 700 mAh/cm2 at a current density of 1 mA/cm2 for 1 h in a symmetric cell. Physical characterizations (XRD and SEM-EDS) showed a thin layer containing Li-Sn alloys along with LiCl formed at the lithium metal surface. Possessing high Li-ion diffusivity, Li-Sn alloyed hybrid anode illustrated a gradual decrease in the charge transfer resistance on increasing the concentration, thus, lower overpotential in symmetric cells, in contrast to pristine Li-metal. However, an increase in the electrical resistance has been observed on increasing the precursor concentration due to the presence of the insulating LiCl phase in the protective layer. Moreover, in-situ optical microscopy demonstrated more uniform and on-surface Li-deposition for the hybrid electrode, whereas mossy and dendritic growth on bare Li-metal. Full cells prepared with Li-Sn alloyed anode against NMC532 cathode illustrated stable cycling up to 150 cycles; contrastingly, the cell with pristine Li-metal showed a drastic capacity fade just after 100 cycles, demonstrating the inclination towards safer lithium metal batteries.

Three-Dimensional Transient Electric Field Characteristics of High Pressure Electrode Boilers

An uneven electric field during the operation of an electrode boiler will lead to the emergence of a high field strength area and low field strength area in the furnace, which will endanger the safe and reliable operation and heating efficiency of the electrode boiler. A numerical study of three-dimensional transient electric field distribution characteristics in a 10 kV high-voltage electrode boiler was carried out. The distribution characteristics of the global electric field of the electrode boiler under the nominal voltage of 10 kV were studied, and the distribution law of the electric field of the electrode boiler under poor power quality, such as different bus voltage and three-phase voltage imbalance, was explored. The results show that the electric field distribution characteristics of the three-phase transient are more obvious in the section closer to the electrode disc, and the electric field distribution is the most uniform in the section that is 1.4 m away from the furnace water. In the case of poor power quality, such as different bus voltage and three-phase voltage imbalance, the points of the maximum electric field intensity of the four surfaces change periodically with time, and the greater the bus voltage fluctuation, the more severe the impact on the transient electric field. The three-phase voltage imbalance will shift the peak value of the electric field intensity. The decrease or offset of electric field intensity in the electrode boiler caused by poor power quality will directly affect its heating efficiency. The electric field simulation results have a specific reference value for improving the internal electric field distribution and on-site operation and maintenance of the electrode boiler.

Dual-functional ionic liquids additive enables dendrite-free Zn anode with ultra-long cycle life over one year

Zn anodes suffer from the formation of uncontrolled dendrites aggravated by the uneven electric field and the insulating by-product accumulation in aqueous zinc-ion batteries (AZIBs). Here, an effective strategy implemented by 1-butyl-3-methylimidazolium hydrogen sulfate (BMIHSO4) additive is proposed to synergistically tune the crystallographic orientation of zinc deposition and suppress the formation of zinc hydroxide sulfate for enhancing the reversibility on Zn anode surface. As a competing cation, BMI+ is proved to preferably adsorb on Zn-electrode compared with H2O molecules, which shields the “tip effect” and inhibits the Zn-deposition agglomerations to inducing the horizontal growth along Zn (002) crystallographic texture. Simultaneously, the protonated BMIHSO4 additives could remove the detrimental OH– in real-time to fundamentally eliminate the accumulation of 6Zn(OH)2·ZnSO4·4H2O and Zn4SO4(OH)6·H2O on Zn anode surface. Consequently, Zn anode exhibits an ultra-long cycling stability of one year (8762 h) at 0.2 mA cm−2/0.2 mAh cm−2, 3600 h at 2 mA cm−2/2 mAh cm−2 with a high plating cumulative capacity of 3.6 Ah cm−2, and a high average Coulombic efficiency of 99.6 % throughout 1000 cycles. This work of regulating Zn deposition texture combined with eliminating notorious by-products could offer a desirable way for stabilizing the Zn-anode/electrolyte interface in AZIBs.

Stretchable Zn‐Ion Hybrid Capacitor with Hydrogel Encapsulated 3D Interdigital Structure

AbstractTo enhance the areal energy density of current flexible energy storage devices, hybrid capacitors combining the advantages of supercapacitors and batteries are proposed and further enhanced by incorporating the 3D interdigital structure design. However, uneven electric field distribution and hindered ion diffusion kinetics due to the non‐electroactive components in these devices limit the enhancement of areal electrochemical performances when expanding the electrodes longitudinally. Herein, hydrogels with high ionic conductivity and high mechanical stability are designed to accommodate Zn2+‐containing electrolytes and integrated with Ti3C2Tx‐MXene electrodes to assemble flexible Zn‐ion hybrid capacitors (ZIHCs). Fully encapsulated by ionic conductive hydrogels, 3D interdigital electrodes enable omnidirectional ion transport and unimpeded ionic accessibility, facilitating adequate electrode reactions, rapid energy storage, and uniform energy distribution. Hence, the all‐hydrogel‐encapsulated ZIHC achieved a 50‐fold increase in capacitance with a quadrupled electrode thickness, exhibiting a large areal capacitance of 1432 mF cm−2 and an energy density of 389.7 µWh cm−2 without sacrificing power density and rate performance. Finite element simulations further illustrate the uniform distribution of potential, electric field intensity, and energy density in this structure. In addition, the device shows great stability under deformation, excellent adhesion, and underwater workability, demonstrating great promise for next‐generation wearable energy storage devices.

Atomic Zincophilic Sites Regulating Microspace Electric Fields for Dendrite-Free Zinc Anode.

Aqueous Zn metal batteries are promising candidates for large-scale energy storage due to their intrinsic advantages. However, Zn tends to deposit irregularly and forms dendrites driven by the uneven space electric field distribution near the Zn-electrolyte interphase. Herein it is demonstrated that trace addition of Co single atom anchored carbon (denoted as CoSA/C) in the electrolyte regulates the microspace electric field at the Zn-electrolyte interphase and unifies Zn deposition. Through preferential adsorption of CoSA/C on the Zn surface, the atomically dispersed Co-N3 with strong charge polarization effect can redistribute the local space electric field and regulate ion flux. Moreover, the dynamic adsorption/desorption of CoSA/C upon plating/stripping offers sustainable long-term regulation. Therefore, Zn||Zn symmetric cells with CoSA/C electrolyte additive deliver stable cycling up to 1600h (corresponding to a cumulative plated capacity of 8 Ah cm-2 ) at a high current density of 10mA cm-2 , demonstrating the sustainable feature of microspace electric field regulation at high current density and capacity.

Improved Separation in Horizontal Protein SDS-PAGE with Double-Deck Flat Electrodes and a Field Inversion Gel Electrophoresis Module.

The horizontal flatbed electrophoresis method is employed to separate protein samples, providing greater flexibility for various electrophoretic applications and easier sample loading compared to its vertical counterpart. In the currently available equipment setup, cathode and anode electrodes are positioned on top of a gel at each end. Since an electric field enters the gel from the top, its strength gradually weakens from the top to the bottom of the gel. When examining the interior of gels following electrophoretic separation, the uneven electric field causes the protein bands to lie down forward in the direction of migration, leading to an increase in bandwidth. This issue has remained unaddressed for several decades. To address this problem, new clamp-shaped and double-deck electrodes were developed to apply an electric field simultaneously from both the top and bottom of the gel. Both of these new electrodes facilitated the formation of perpendicular protein band shapes and enhanced resolution at a comparable level. Due to their ease of use, double-deck electrodes are recommended. By combining these new electrodes with the field inversion gel electrophoresis (FIGE) technique, the protein bands could be focused and aligned nearly vertically, resulting in the highest level of electrophoretic resolution. Our electrodes are compatible with polyacrylamide gels of varying sizes, buffer systems, and sample well formats. They can be easily manufactured and seamlessly integrated into existing laboratory instruments for practical use.

Flashing ratchet effect for driving carriers to accelerate directional migration in organic photovoltaic devices

The organic electron flashing ratchet experiment describes the phenomenon in which an electric current can be detected, even in the absence of a net potential bias. To understand the experimental mechanism at the quantum level, we utilize the quantum nonadiabatic method to simulate the electron dynamics in an organic polymer chain with the flashing ratchet potential. It is found that electrons exhibit directional migration with a velocity, which depends on both the asymmetry and the flashing frequency of the ratchet potential. In addition, the flashing ratchet, which describes the non-uniform and time-varying electric field, increases the velocity by 58.6% compared to the uniform electric field. The flashing ratchet effect exists intrinsically in actual organic photovoltaics (OPVs), due to the naturally uneven and time-varying inherent electric field caused by various inevitable factors in bulk heterojunctions (BHJ). Moreover, the ratchet potential can be artificially constructed by designing the morphology of the BHJ, which opens a promising avenue for driving electrons to accelerate directional migration, and improving the photoelectric conversion efficiency of OPVs.

An improved resistance model of positive subsonic plasma channels in water

The subsonic plasma channel and water can be regarded as series resistors in the pre-breakdown stage of sub-millisecond pulsed discharge in conductive water. An improved resistance model of the positive subsonic plasma channel is proposed. The gap resistance and the morphology of the bubble cluster and the plasma channel inside it are obtained from the electrical measurement and optical observation, respectively. The resistance of the plasma channel in the strong-ionization stage is calculated using the small-current arc resistance model. The improved model of the water resistance is established by analyzing the relationship between its equivalent cross-sectional area and its length in an uneven electric field. The resistance of the plasma channel in the weak-ionization stage is calculated. The resistance, voltage, and energy in the gap are analyzed based on the improved resistance model. The plasma channel's resistance is far less than the water resistance. The low voltage drop in the plasma channel leads to a high electric potential in the plasma channel's head, which is conducive to the plasma channel's development. 97% of the total energy in the pre-breakdown stage is consumed by the water resistor. The improved resistance model is helpful to supplement the development mechanism of the sub-millisecond pulsed discharge in water.

Preparation of anode by MOF pyrolysis enabled long-life rechargeable zinc nickel batteries

Water-induced parasitic reaction and zinc dendrite growth caused by uneven electric field distribution on the surface of the zinc anode are the most controversial problems in the practical application of zinc-nickel rechargeable batteries in large-scale energy storage. Herein, Bi2O3/In2O3 doped ZnO@C synthesized by MOF pyrolysis with good cycle stability. The ability to inhibit hydrogen evolution and achieve uniform deposition of zinc is characterized by CV, Tafel, and scanning electron microscopy (SEM). Benefiting from the high hydrogen evolution overpotential and high electrical conductivity, Bi2O3 doped ZnO@C (BCZ) and In2O3 doped ZnO@C (ICZ) electrodes deliver high capacity of 640 mA h g−1 and 580 mA h g−1 at 10 C after 1200 and 3400 cycles, respectively, and reveals long-term cyclic stability with capacity retention over 90%. This work provides new ideas for the anode synthesis of aqueous rechargeable zinc metal batteries and other batteries.

Study of electrical properties and detection mechanism of a practical novel 3D-Spherical Electrode Detector

Among the 3D electrode Si detectors for high energy particle and X-ray detection, the traditional 3D-Trench electrode Si detector is a semiconductor detector that is widely used and discussed. Aiming at removing the shortcomings of the traditional 3D-Trench electrode Si detectors such as uneven electric field distribution, asymmetric electric potential, and the existence of some dead zone, we propose a new type 3D-Spherical Electrode Detectors and carry out extensive and systematic studies of their physical properties. We simulated detector electric field, electric potential, electron concentration distribution, full depletion voltage, leakage current, capacitance, the incident particle induced transient current and the weighting field. We systematically studied and analyzed detector’s electrical characteristics. By comparing with the traditional 3D-Trench electrode Si detectors, the new detector structure has more uniform electric field and potential, and less depletion voltage, leakage current and capacitance.

Few-layer Graphene Lithiophilic and Sodiophilic Diffusion Layer on Porous Stainless Steel as Lithium and Sodium Metal Anodes.

In order to subdue the obvious problem of uneven electric field distribution on regularly used copper/aluminum current collectors for alkali metal batteries, graphene on porous stainless steel (pSS_Gr) was fabricated using the ion etching technique that is employed as an effective host for lithium and sodium metal anodes. The binder-free pSS_Gr demonstrated stable Li plating and stripping at areal current and capacity of 6 mA cm-2 and 2.54 mAh cm-2 , respectively, for over 1000 cycles with 98% coulombic efficiency (C.E.). Also, in the case of Na metal anode, the host has shown stable performance at 4 mA cm-2 and 1 mAh cm-2 over 1000 cycles with ∼100% C.E.. Further, a full cell composed of Li-plated pSS_Gr as an anode and LiFePO4 as a cathode is electrochemically tested at 50 mA g-1 current density with stable 100 cycles.

The Generation and Migration of Bubbles in Oil-Pressboard Insulation Needle-Plate System

Bubbles in transformer oil can easily lead to partial discharge (PD), which can deteriorate the transformer oil and even breakdown the transformer insulation. To clarify the migration process and the characteristics of bubbles generated in an oil-immersed power transformer exposed to an extremely uneven electric field, we experimentally monitor these phenomena under an extremely nonuniform ac electric field and numerically simulate the migration distance and the migration speed of bubbles with different initial positions and sizes. The results show that the streamer discharge channel formed by a PD in oil is gasified into a bubble channel. After it collides with the surface of the pressboard, its morphology is transformed into approximately spherical bubbles due to the surface tension of the gas–liquid interface. After bubbles are generated in the oil, they move away from areas with a strong electric field due to the electric-field force and gradually approach the oil surface due to the buoyancy force. The experimental results are consistent with the simulation results, which verify the rationality of the simulation model.

Study on surface discharge characteristics and design method of large size oil-paper insulation of electrical transformer

When partial discharge occurs in the power transformer, the arc can further develop on the oil-paper interface between high and low potentials, and then form a path, resulting in large-area flashover. This will lead to a wide range of insulation damage, insulation failure, equipment shutdown and even large-scale economic losses. For the insulation damage caused by surface discharge of oil paper insulation, relevant scientific research institutions have carried out a large number of experimental studies. However, limited by the test conditions, the research focuses on the small-size model below 50mm, and mostly adopts the test device of uneven electric field. The research on the “large-size“ of the same scale inside the transformer is still blank. In this study, an oil-paper insulation surface discharge test platform with a large size of 50-150mm is built, the electric field conditions at the oil paper interface during the operation of transformers in engineering are simulated, and the surface discharge test of insulating paperboard is carried out by taking the same sample processing means as the engineering. Combined with the test results, a typical design optimization case of setting along surface corner ring to improve the allowable value of along surface discharge field and enhance along surface insulation margin is proposed. It lays a foundation for enriching the transformer oil-paper insulation design parameter system and improving the transformer oil paper insulation performance and operation reliability.

Ultra‐Stable Aqueous Zinc Batteries Enabled by β‐Cyclodextrin: Preferred Zinc Deposition and Suppressed Parasitic Reactions

AbstractThe intrinsic zinc dendrite growth aggravated by the uneven electric field at the Zn anode surface and the water‐induced parasitic reactions have largely impeded rechargeable aqueous zinc‐ion batteries for the practical applications in large‐scale energy storage. Here, an effective strategy is proposed to manipulate Zn deposition and simultaneously prevent the generation of insulating by‐products (Zn4SO4(OH)6·xH2O) for improved plating/stripping on Zn anodes by the addition of a nontoxic electrolyte additive, β‐cyclodextrin (β‐CD). The simulation results indicate that β‐CD molecules prefer to adsorb horizontally on Zn (002) plane, regulating the diffusion pathways and deposition sites of Zn2+ for the preferred Zn deposition along (002) plane without dendrite formation and inhibiting the H2 generation and the formation of Zn4SO4(OH)6·xH2O by facilitating desolvation of [Zn(H2O)6]2+. Consequently, an ultra‐long stable cycling up to 1700 h at a high current density of 4 mA cm−2 can be achieved by the addition of β‐CD, 17 times that of the pure ZnSO4 electrolyte and the remarkable stability is also maintained under harsh test condition (40 mA cm−2, 20 mAh cm−2). This study highlights the important role of β‐CD in engineering the interfacial stability during Zn plating/stripping for high‐performing aqueous batteries.

Simulation of the electric field of a polymer bushing in the Ansys Maxwell software environment

The article analyses the software tools for modelling the maps of the electric field strength of insulators. The need to address this issue is dictated by the fact that the uneven electric field on the insulators increases the probability of partial discharges that destroy the insulating layer, so it is very important to optimize the electric field strength on the insulator. The design features of bushings and features of partial discharges in them are considered. The distribution of electric field strength in a polymer pass-through operating in an AC network without contaminants is considered. The results of modelling the electric field of insulators in the software environment Ansys Maxwell, which is based on the simulation of the finite element method, are presented. Points in the construction of a 35 kV bushing polymer insulator have been identified, where the highest level of electric field strength is concentrated. A method of influencing the area under study in the area of the flange connection to the ground plate is proposed. This defines the use of a conductive cover placed between the flange and the place of connection to the polymeric insulating layer, which significantly improves the overall electric field strength distribution on the surface of the bushing polymer insulator and makes it competitive compared to the most commonly used porcelain bushings, by increasing the electrical strength of the structure. According to the results of research, a means of optimizing the electric field of the pass-through polymer insulator is proposed, which allows to increase its electric resistance and reduce the electric field strength in the area of flange contact with the mounting surface, which in turn prevents premature partial discharges in the insulating bodies.

Multi-mesa photodiodes with uneven electric field distribution designed for 100-Gbits 4-level pulse amplitude modulation applications

The influence of a multi-mesa structure on a pin photodiode (pin-PD) was carefully studied. It was found that PDs with multi-mesa structures form an uneven electric field in the device under the working voltage, and the electron obtains the overshoot velocity in the uneven electric field. The device that adopts the multi-mesa structure can also reduce the capacitance. The introduction of multi-mesa structures provides another way to improve the performance of the pin-PD. Compared with the one-mesa structure, the multi-mesa structure improved the bandwidth of 5.5 GHz and reduced the capacitance from 26 to 19 fF. The modified pin-PD with a multi-mesa structure can be used in 100-Gbits optical communication systems.