Charging Mechanism Research Articles

The Opto‐Ionic Voltage Effect Soft Triode: An Optical‐To‐Ionic Signal Converter

AbstractA novel opto‐ionic device based on the recently reported Ionic Voltage Effect Soft Triode (IVEST) is introduced. This device can convert optical to ionic signals as it is shown here. The characterization of the opto‐IVEST points to an optically induced charging mechanism and to various potential applications. The opto‐IVEST shows the ability to detect and memorize optical signals. Furthermore, the device exhibits learning behavior and a hybrid logic gate function.

Operando Raman observation of lithium-ion battery graphite composite electrodes with various densities and thicknesses

Understanding the mechanisms of inhomogeneous charging and discharging reactions in an electrode is critical to improving the rate capability of lithium-ion batteries. Various methods have been developed to observe the distribution of electrode structure or lithium ions within an electrode; however, most of these methods require large-scale equipment or entail complex procedures. To simplify reaction distribution measurements within electrodes, this study developed specially designed cells and conducted operando observations of reaction distribution in graphite composite electrodes using Raman spectroscopy. Behaviors on both the electrolyte and current collector sides of the electrodes were compared, and electrodes of various densities and thicknesses were examined. For electrodes with low density, the changes in graphite structure were almost simultaneous on the electrolyte and current collector sides and were hardly dependent on the electrode thickness. In contrast, the changes in electrode structure with increased density were dependent on their thickness. This implies that the ion transportation length is responsible for the reaction distribution in the electrodes when ion channels connecting the current collector and electrolyte sides decrease owing to the increased electrode density. The simple method developed in this study is expected to further contribute to the understanding of the distribution of reactions within graphite composite electrodes.

Ferrimagnetic pseudocapacitive MnFe2O4 electrodes and supercapacitor devices

This investigation is motivated by the surge of interest in materials, combining high spontaneous magnetization and pseudocapacitance at room temperature. Ferrimagnetic MnFe2O4 offers benefits of high magnetization. However, the non-pseudocapacitive behavior, low capacitance and high resistance of MnFe2O4 are limiting factors for its applications in magnetic pseudocapacitive devices. This investigation demonstrates that nearly ideal pseudocapacitive behavior can be achieved for MnFe2O4 electrodes in Na2SO4 electrolyte. High pseudocapacitance is observed in positive and negative potential ranges and two different charging mechanisms are proposed. High capacitance is achieved at a low impedance. The ability to achieve comparable and high areal capacitances in the positive and negative potential ranges facilitates the fabrication of a symmetric pseudocapacitive device, containing ferrimagnetic MnFe2O4 as cathode and anode material for operation in enlarged voltage window of 1.6 V. The symmetric device shows capacitance of 0.92 F cm−2 at a current density of 3 mA cm−2. The individual electrodes and device show good cycling stability. The approach is based on the use of murexide and gallocyanine as redox-active dispersants and charge transfer mediators. The analysis of testing results provides an insight into the influence of chemical structure, charge and redox properties of the dispersants on the capacitive behavior. The ability to fabricate a pseudocapacitive device, containing two ferrimagnetic electrodes is promising for energy storage, water purification and novel applications based on magnetocapacitive effects.

To DISP or Not? The Far‐Reaching Reaction Mechanisms Underpinning Lithium‐Air Batteries

AbstractThe short history of research on Li−O2 batteries has seen a remarkable number of mechanistic U‐turns over the years. From the initial use of carbonate electrolytes, that were then found to be entirely unsuitable, to the belief that (su)peroxide was solely responsible for degradation, before the more reactive singlet oxygen was found to form, to the hypothesis that capacity depends on a competing surface/solution mechanism before a practically exclusive solution mechanism was identified. Herein, we argue for an ever‐fresh look at the reported data without bias towards supposedly established explanations. We explain how the latest findings on rate and capacity limits, as well as the origin of side reactions, are connected via the disproportionation (DISP) step in the (dis)charge mechanism. Therefrom, directions emerge for the design of electrolytes and mediators on how to suppress side reactions and to enable high rate and high reversible capacity.

DISP oder nicht? Die weitreichenden Reaktionsmechanismen, die den Lithium‐Luft‐Batterien zugrunde liegen

AbstractIn der kurzen Geschichte der Forschung an Li−O2‐Batterien gab es im Laufe der Jahre eine bemerkenswerte Anzahl mechanistischer Kehrtwendungen. Von der anfänglichen Verwendung von Karbonat‐Elektrolyten, die sich dann als völlig ungeeignet erwiesen, über die Annahme, dass (Su)Peroxid allein für die Degradation verantwortlich sei, bevor man feststellte, dass sich der reaktivere Singulett‐Sauerstoff bildet, bis hin zu der Hypothese, dass die Kapazität von einem konkurrierenden Oberflächen‐/Lösungsmechanismus abhängt, bevor ein praktisch ausschließlicher Lösungsmechanismus identifiziert wurde. Wir plädieren hier für einen immer neuen Blick auf die vorliegenden Daten ohne Voreingenommenheit gegenüber vermeintlich etablierten Erklärungen. Wir erläutern, wie die neuesten Erkenntnisse über Raten‐ und Kapazitätsgrenzen sowie die Entstehung von Nebenreaktionen über den Disproportionierungsschritt (DISP) im (Ent‐)Ladungsmechanismus miteinander verbunden sind. Daraus ergeben sich Hinweise für das Design von Elektrolyten und Mediatoren, wie Nebenreaktionen unterdrückt und hohe Raten und hohe reversible Kapazitäten ermöglicht werden können.

Age of information minimization in UAV-assisted data harvesting networks by multi-agent deep reinforcement curriculum learning

Unmanned Aerial Vehicles (UAVs) are increasingly being used for data harvesting from Wireless Sensor Nodes (SNs). This study aims to minimize the Age of Information (AoI) during data collection, while also considering the energy sustainability of the UAVs. Addressing the challenge of optimizing performance in Multi-Agent Reinforcement Learning (MARL) systems as the number of agents increases, our study introduces a MARL approach combined with curriculum learning and evolutionary strategy. This innovation specifically targets the performance issue in traditional MARL setups when scaling up the number of agents. By applying curriculum learning and evolutionary strategies, our method not only enhances MARL scalability but also integrates energy-efficient charging mechanisms, effectively enhancing system performance in large-scale deployments. Numerical results show that our proposed algorithm outperforms baselines in terms of AoI and charging, proving its effectiveness in managing the complexities of large-scale MARL systems.

Enhancing capacitance performance of functional group assisted carbon quantum dots derived from turmeric plant waste

Supercapacitors have attracted significant attention in modern devices as a promising solution for electrical energy storage due to their remarkable capability to undergo rapid charge and discharge cycles. While various materials are employed in the construction of supercapacitors, carbon-based materials emerge as a predominant choice within the commercial realm. In present report, our intention is to develop an effective supercapacitor device derived from natural biomass. Therefore, we have synthesized water soluble, monodisperse and fluorescent carbon quantum dots (CQDs) from turmeric leaves (Curcuma caesia) via a single step hydrothermal carbonization. Further, the doctor blade technique was employed to coat a layer of CQDs on stainless steel substrate using PVA as a binder. We observed the functional groups associated with QDs triggers the fast diffusion of ions and transmission of electrons with conducting substrate and electrolyte and thereby effectively charge and discharge mechanism. The supercapacitor based on carbon quantum dots (CQDs) based electrode exhibits exceptional performance characteristics with a remarkable specific capacitance of 468 F/g and highest energy density of 78.6 Wh/kg, superior to the values reported for most carbon-based supercapacitors. Further, we demonstrated the light dependent capacitive enhancement by depositing a thin P3HT layer over CQDs. Moreover, CQDs-based supercapacitor achieves a maximum power density of 733.2 W/kg when operated in a 1 M KOH electrolyte solution and an excellent capacitive retention of about 80 % even after 5000 cycles.

Research on the Orderly Charging and Discharging Mechanism of Electric Vehicles Considering Travel Characteristics and Carbon Quota

Research on the Orderly Charging and Discharging Mechanism of Electric Vehicles Considering Travel Characteristics and Carbon Quota

Performance Projection of Vacuum Gate Dielectric Doping-Free Carbon Nanoribbon/Nanotube Field-Effect Transistors for Radiation-Immune Nanoelectronics.

This paper investigates the performance of vacuum gate dielectric doping-free carbon nanotube/nanoribbon field-effect transistors (VGD-DL CNT/GNRFETs) via computational analysis employing a quantum simulation approach. The methodology integrates the self-consistent solution of the Poisson solver with the mode space non-equilibrium Green's function (NEGF) in the ballistic limit. Adopting the vacuum gate dielectric (VGD) paradigm ensures radiation-hardened functionality while avoiding radiation-induced trapped charge mechanisms, while the doping-free paradigm facilitates fabrication flexibility by avoiding the realization of a sharp doping gradient in the nanoscale regime. Electrostatic doping of the nanodevices is achieved via source and drain doping gates. The simulations encompass MOSFET and tunnel FET (TFET) modes. The numerical investigation comprehensively examines potential distribution, transfer characteristics, subthreshold swing, leakage current, on-state current, current ratio, and scaling capability. Results demonstrate the robustness of vacuum nanodevices for high-performance, radiation-hardened switching applications. Furthermore, a proposal for extrinsic enhancement via doping gate voltage adjustment to optimize band diagrams and improve switching performance at ultra-scaled regimes is successfully presented. These findings underscore the potential of vacuum gate dielectric carbon-based nanotransistors for ultrascaled, high-performance, energy-efficient, and radiation-immune nanoelectronics.

Molecular dynamics simulations of ionic liquids confined into MXenes

Two-dimensional (2D) transition metal carbides known as MXenes have been extensively investigated as electrode material of electrochemical devices, including supercapacitors. Here we present a detailed computational study of ionic liquids in contact with Ti3C2F2, both at planar surface and under confinement. The simulations employ an extension of the constant potential model (CPMχ) that can properly deal with materials composed of chemical elements with different electronegativities. The average partial charges of MXene atoms calculated with CPMχ are in excellent agreement with the ones obtained by DFT calculations. The differential capacitance and the charging mechanisms are thoroughly analyzed for two ionic liquids with a common cation, [EMIM][BF4] and [EMIM][NTf2]. By varying the MXene interlayer dimension, the best performance in terms of charge storage is obtained in electrodes with 12.6 Å spacing, with outperformance of [EMIM][BF4]-based cells.

Recent Advances in Ferroelectret Fabrication, Performance Optimization, and Applications.

The growing demand for wearable devices has sparked a significant interest in ferroelectret films. They possess flexibility and exceptional piezoelectric properties due to strong macroscopic dipoles formed by charges trapped at the interface of their internal cavities. This review of ferroelectrets focuses on the latest progress in fabrication techniques for high temperature resistant ferroelectrets with regular and engineered cavities, strategies for optimizing their piezoelectric performance, and novel applications. The charging mechanisms of bipolar and unipolar ferroelectrets with closed and open-cavity structures are explained first. Next, the preparation and piezoelectric behavior of ferroelectret films with closed, open, and regular cavity structures using various materials are discussed. Three widely used models for predicting the piezoelectric coefficients (d33) are outlined. Methods for enhancing the piezoelectric performance such as optimized cavity design, utilization of fabric electrodes, injection of additional ions, application of DC bias voltage, and synergy of foam structure and ferroelectric effect are illustrated. A variety of applications of ferroelectret films in acoustic devices, wearable monitors, pressure sensors, and energy harvesters are presented. Finally, the future development trends of ferroelectrets toward fabrication and performance optimization are summarized along with its potential for integration with intelligent systems and large-scale preparation.

Pyrolysis of spent coffee grounds dispersed clay in N2: Production of type-II conductive ceramics with electrochemical performance

Pyrolysis of spent coffee grounds dispersed clay in N2 produces type-II conductive ceramics with electrochemical performance. Protective atmosphere and surface screening play important roles in converting spent coffee grounds into carbon coatings on ceramic surfaces; the former prevents oxidation of organic ingredients and confinement of pyrolysis in clay for the latter. Selective-area electrical measurements indicate resultant ceramics to be conductive and interconnected carbon coatings are further verified by SEM inspections and consistency between thermal conductivity and diffusivity. Conductive ceramics show a high usage of surface area by electric double layer charging mechanism thus giving an excellent electrochemical performance.

Modular, Vision-Based Control of Automated Charging Systems for Electric Vehicles

Contemporary vehicle fleets include a variety of both manually and automated operated vehicles. A significant shift involves the increasing use of electric powertrains. However, the current electric charging infrastructure predominantly relies on manual processes. There is an opportunity to automate the charging process for these cars, with the intent to enhance convenience, aid people with accessibility needs, to support MW charging where EV cables are heavy, and finally to enable autonomous driving. The charging standards are common but the mechanisms to access the charging ports are not i.e., lids and protectives. This could be a challenge in the automation process given the complexity of the manipulation task at hand. With the increasing variety of electric vehicle models, standardizing charging mechanisms becomes imperative to streamline the charging process and enable broader adoption. In summary, this paper presents a holistic approach to addressing the evolving needs of electric vehicle charging infrastructure, emphasizing the importance of automation in enabling efficient, accessible, and future-ready charging solutions.

MC³: A Multicharger Cooperative Charging Mechanism for Maximizing Surveillance Quality in WRSNs

MC³: A Multicharger Cooperative Charging Mechanism for Maximizing Surveillance Quality in WRSNs

Clothing comfort sensing system based on triboelectric and tribological behavior of fabrics

Static electricity accumulated on fabrics often causes discharged discomfort, fire, explosion, and cardiovascular diseases. Meanwhile, the electricity can be harvested and used for self-powered wearable devices. Therefore, it is essential to regulate fabric triboelectricity through studying the relationship between friction coefficients and triboelectric charges. In this paper, a reciprocating tribometer coupled with triboelectric testing instruments is designed to collect in-situ tribological and triboelectric properties for laterally sliding fabric based triboelectric nanogenerators (F-TENGs). In this case, the regulation factors involve motion conditions (including load, frequency, friction angle, etc.), surface components and environments. The results show that faster sliding speed and lower humidity produce higher triboelectric outputs of F-TENGs. Especially, amino groups modified silk shows an extremely strong electron-donating ability and achieves a high triboelectric current of 382.2 nA when paired with polyimide, which is enhanced by 1.67 times compared with silk. Most importantly, the friction coefficient values of F-TENGs show almost the same trend as the triboelectric outputs. Based on this, a sensing system for monitoring comfort level of fabrics is successfully designed through rubbing tested fabrics and observing indicator lamps. This work proposes a tribological approach with valuable insights of the underlying mechanism of triboelectric charging and extended applications.

Understanding Electrolyte Ion Size Effects on the Performance of Conducting Metal-Organic Framework Supercapacitors.

Layered metal-organic frameworks (MOFs) have emerged as promising materials for next-generation supercapacitors. Understanding how and why electrolyte ion size impacts electrochemical performance is crucial for developing improved MOF-based devices. To address this, we investigate the energy storage performance of Cu3(HHTP)2 (HHTP = 2,3,6,7,10,11-hexahydroxytriphenylene) with a series of 1 M tetraalkylammonium tetrafluoroborate (TAABF4) electrolytes with different cation sizes. Three-electrode experiments show that Cu3(HHTP)2 exhibits an asymmetric charging response with all ion sizes, with higher energy storage upon positive charging and a greater charging asymmetry with larger TAA+ cations. The results further show that smaller TAA+ cations demonstrate superior capacitive performances upon both positive and negative charging compared to larger TAA+ cations. To gain further insights, electrochemical quartz crystal microbalance measurements were performed to probe ion electrosorption during charging and discharging. These reveal that Cu3(HHTP)2 has a cation-dominated charging mechanism, but interestingly indicate that the solvent also participates in the charging process with larger cations. Overall, the results of this study suggest that larger TAA+ cations saturate the pores of the Cu3(HHTP)2-based electrodes. This leads to more asymmetric charging behavior and forces solvent molecules to play a role in the charge storage mechanism. These findings significantly enhance our understanding of ion electrosorption in layered MOFs, and they will guide the design of improved MOF-based supercapacitors.

Power hardware-in-loop emulation of a battery for charging systems and grid applications

Relevance. Batteries are playing an increasingly vital role in power systems due to their utilization in various applications including microgrids, electric vehicles, sustaining geographically isolated communities, and energization of automated devices. Since they are considered as the enabling technology for renewable energy integration, the absence of battery systems from islanded microgrids can result in decreased system reliability and compromised performance due to the intermittency of local sources. Nevertheless, the hazardousness associated with their charging mechanism has led to the urgent continuous development of charging technologies and battery management systems. Aim. To develop a safe testbed to examine the functionality of newly produced battery charging stations and battery managers without employing actual physical batteries to avoid the hazardous manipulation of batteries and increase flexibility during the design and validation stage. This is accomplished by modeling the electrochemical dynamics of the battery system and integrating the device-under-test to a DC converter, which reacts based on these modeled dynamics. Novelty. This work adapts one of the most successful Li-ion battery models available in the literature and utilizes it to interact with power electronic devices that exchange power signals. Unlike other work in this field, the design is based on power hardware-in-loop principles and has minimized power consumption characteristics due to its unique configuration. The constructed computer model can be easily reparametrized to describe the dynamics of various battery capacities. Methods. MATLAB-based simulations of the proposed testbed were conducted for high and low power capacity. A LabView-based program was interfaced with the testbed hardware using a NI-DAQ board to validate the proposed design practically. The testbed hardware components were entirely developed from scratch for experimentation purposes. Results. The proposed testbed successfully imitated the dynamics of the battery, while the practical results concurred the simulated ones.

Charge Storage Properties of Ferrimagnetic BaFe12O19 and Polypyrrole-BaFe12O19 Composites.

This investigation is motivated by an interest in multiferroic BaFe12O19 (BFO), which combines advanced ferrimagnetic and ferroelectric properties at room temperature and exhibits interesting magnetoelectric phenomena. The ferroelectric charge storage properties of BFO are limited due to high coercivity, low dielectric constant, and high dielectric losses. We report the pseudocapacitive behavior of BFO, which allows superior charge storage compared to the ferroelectric charge storage mechanism. The BFO electrodes show a remarkably high capacitance of 1.34 F cm-2 in a neutral Na2SO4 electrolyte. The charging mechanism is discussed. The capacitive behavior is linked to the beneficial effect of high-energy ball milling (HEBM) and the use of an efficient dispersant, which facilitates charge transfer. Another approach is based on the use of conductive polypyrrole (PPy) for the fabrication of PPy-BFO composites. The choice of new polyaromatic dopants with a high charge-to-mass ratio plays a crucial role in achieving a high capacitance of 4.66 F cm-2 for pure PPy electrodes. The composite PPy-BFO (50/50) electrodes show a capacitance of 3.39 F cm-2, low impedance, reduced charge transfer resistance, enhanced capacitance retention at fast charging rates, and good cyclic stability due to the beneficial effect of advanced dopants, HEBM, and synergy of the contribution of PPy and BFO.

Study on time–frequency features of induced charge signals during the damage and failure process of coal medium

Monitoring and preventing coal-rock dynamic disasters are vital for safe mining. To investigate the time–frequency features of induced charge signals with coal damage and failure of roadways, the generation mechanism of free charge in loaded coal is analyzed and the induced charge monitoring test is conducted. According to the stress-induced charge-time curves, the time-domain features of charge signals at each loading stage are obtained. The wavelet threshold denoising approach and generalized Morse wavelet transform method are applied to denoise the raw signals and study the frequency-domain features. Further, the quantitative relationship between the de-noised induced charge signals and the degree of coal damage is established. The results show that the event number, amplitude and fluctuation degree of available induced charge signals are all at a low level in the compaction and elastic stages of the coal, which are mainly generated by the piezoelectric effect and predominantly represent discreteness. When entering the plastic and failure stages, the available signals are primarily produced by the crack propagation and triboelectric effects, with a significant increase in the event number, amplitude, and fluctuation degree. Then the induced charge signals gradually transit from discrete to continuous. Generally, the dominant frequency of the available induced charge signals during the coal damage process is concentrated at 0 ~ 11 Hz. The available induced charge is positively correlated with the degree of coal damage, which can perform the damage degree of coal mass, providing a new approach to evaluate the stability of roadway surrounding rocks.

Simulating the charging mechanism of a realistic nanoporous carbon-based supercapacitor using a fully polarizable model

Nanoporous carbon-based supercapacitors are established energy storage devices, that complement Li-ion batteries in high-power applications. So far, the study of these systems through simulations required drastic simplification of the electrolyte and/or of the electrode. In this work, we use state-of-the-art constant potential classical molecular dynamics simulations, where both the electrode and the electrolyte are polarizable, to study complex carbide-derived carbons with 1-ethyl-3-methylimidazolium bis(trifluoromethane)sulfonyl imide ionic liquid electrolyte. We show that using this set-up allows to obtain integral capacitances (i.e. the main property to characterize supercapacitors) in quantitative agreement with experiments. The simulations, performed in a range of applied potentials of 1V to 4V, then provide microscopic details on the charging mechanism, revealing that it is not symmetrical between the positive and negative electrodes. A pure exchange of ions is observed on the positive electrode, while an ion exchange combined with cation adsorption takes place on the negative one. Our work shows that accounting for the coupling of electrode and electrolyte polarization improves the accuracy of the results, opening the way toward a more quantitative comparison with experiments.