Capacitance Loss Research Articles

Prediction of Temperature Variability on Power Transmission Line Parameters using Intelligent Approaches

Due to changes in meteorological factors, the instability in the power at the end of the transmission system demands considerable attention. The temperature of the transmission line varies, which has a significant impact on the line parameters. An accurate prediction of line parameters behaviour is necessary to ensure system reliability. The present study is a step towards predicting variations in line parameters with respect to temperature variation. In addition, power loss and voltage drop due to variations in resistance are also predicted. Support Vector Machine (SVM) and ElasticNet, a machine learning algorithm, predict line parameters such as resistance, inductance, capacitance, voltage drop, and power losses. Furthermore, different seasons-based SVM and ElasticNet models for these parameters are considered. Seasons-based models are divided into two types, namely, summer and winter. 220-Kilovolt transmission data and weather information are used as model inputs. Predicted results of transmission line parameters are described in the form of RMSE and MRE. Moreover, the performance results of SVM and ElasticNet are also compared to show better prediction results. The result shows that the minimum prediction error of line parameters are 0.0511, 0.301, 0.426, 0.913, and 0.1501 in RMSE and 4.212, 0.518, 2.888, 0.097, and 0.615 percentages in MRE. This research work may provide technical guidance to transmission line engineers on enhancing the performance of transmission systems.

Porous nitrogen-doped carbons derived from poultry feathers for electrochemical capacitors

The synthesis of a nitrogen doped carbon material (NDCM) from the ball-milling and chemical activation of high temperature carbonised waste chicken feathers is reported. Synthesised NDCMs with nitrogen content ranging from 2.2 to 6.6 wt% were analysed via a range of physio and electrochemical characterisation methods. The effects of carbonisation temperature, mechanical milling and chemical activation were evaluated on specific capacitance and charge retention. Electrochemical testing demonstrated that the optimised NDCM (carbonised at 700 °C followed by ball milling and chemical activation) possessed a specific capacitance of 195 F g−1 at 1 A g−1 current density. At the higher current density of 40 A g−1 89 % of the capacitance is retained. Moreover, this material showed a cycle life of 1000 galvanostatic charge/discharge cycles with a 1 % loss in capacitance at a current density of 5 A g−1.

Ultrasound-assisted fungal self-growth and heteroatom doping for the preparation of high-performance lignocellulose-based supercapacitor electrodes

Biomass materials are widely used as supercapacitor electrode materials due to their cost-effectiveness and eco-friendliness. In this work, ultrasound-assisted impregnation was employed for the thorough mixing of the liquid medium, and fungal treatment was conducted on the three main components of lignocellulose to prepare a fungi-modified heteroatom-doped lignocellulose-based carbon material (LCF-NP). The effects of heteroatom doping, the content of the three main components, and fungal modification on the electrochemical performance of lignocellulose-based carbon materials was investigated. The results revealed the synergistic effect of heteroatom doping and fungal treatment on the electrochemical performance. Compared with its counterpart free of fungal treatment, LCF-NP has a more reasonable pore structure and exhibits excellent electrochemical performance. LCF-NP porous carbon material has the highest specific surface area (792 m2/g), large pore volume (0.523 cm3/g), and ideal specific capacitance (1940 mF/cm2) under the conditions of 1.0 M Na2SO4 electrolyte and current density of 0.5 mA/cm2. After 10,000 cycles, there is almost no loss of capacitance. These results indicate that the joint utilization of heteroatom doping and fungal treatment has a promising application prospect in pore structure regulation and electrochemical performance improvement. This study provides a new strategy for the preparation of lignocellulose-based carbon electrode materials.

Surface Charge Regulation of Graphene by Fluorine and Chlorine Co-Doping for Constructing Ultra-Stable and Large Energy Density Micro-Supercapacitors.

Settling the structure stacking of graphene (G) nanosheets to maintain the high dispersity has been an intense issue to facilitate their practical application in the microelectronics-related devices. Herein, the co-doping of the highest electronegative fluorine (F) and large atomic radius chlorine (Cl) into G via a one-step electrochemical exfoliation protocol isengineered to actualize the ultralong cycling stability for flexible micro-supercapacitors (MSCs). Density functional theoretical calculations unveiled that the F into G can form the "ionic" C─F bond to increase the repulsive force between nanosheets, and the introduction of Cl can enlarge the layer spacing of G as well as increase active sites by accumulating the charge on pore defects. The co-doping of F and Cl generates the strong synergy to achieve high reversible capacitance and sturdy structure stability for G. The as-constructed aqueous gel-based MSC exhibited the superb cycling stability for 500,000 cycles with no capacitance loss and structure stacking. Furthermore, the ionic liquid gel-based MSC demonstrated a high energy density of 113.9mWhcm-3 under high voltage of up to 3.5V. The current work enlightens deep insights into the design and scalable preparation of high-performance co-doped G electrode candidate in the field of flexible microelectronics.

Single, binary, and ternary nanocomposite electrodes of reduced graphene oxide@polyaniline@Co-Prussian analog for supercapacitors

The present work includes fabrication of a binary and ternary and composites of reduced graphene oxide (RGO), Polyaniline (Pani), and cobalt Prussian blue analog (Co-PA) for high performance supercapacitor. The materials were characterized using XRD, SEM, FT-IR, and BET techniques. The results confirm the formation of the desired nanocomposites. The electrochemical properties were evaluated in three electrode configuration using CV, CCD and EIS methods. The ternary composite of RGO@Pani@Co-PA showed better electrochemical properties than that obtained from the binary composites as well as their constituent components. The ternary-based sample had a specific capacitance of 490 Fg-1 at a current density of 1 A g-1 and a minimal capacitance loss of 93.9% after 3000 electric cycles. The ternary composites' remarkable electrochemical performance has been attributed to their well-thought-out, distinctive architecture, which offers a substantial surface area and promotes synergistic effects among the other ingredients. The ternary RGO@Pani@Co-PA composite was used as the anode electrode (positive) and activated carbon as the cathode (negative) materials in the assembly of the asymmetric supercapacitor (ASC) device. Over a wide potential window of 2 V, the fabricated ASC had a remarkable specific energy of 58.9 Wh kg-1 at a specific power of 9210 W kg-1 and 88.5% device capacitance stability after 5000 cycles of charge/discharge.

Relaxor-like behavior of the dielectric response of dense ferroelectric composites

We study experimentally and theoretically the influence of size effects and structural factors on the dielectric and ferroelectric properties of the dense ferroelectric composites. The composites have the form of the tape-casted films with 28 vol% of nanosized or submicron BaTiO3 particles dispersed in the polyvinyl butyral. We measured and analyzed the temperature dependences of the capacitance and dielectric losses in the temperature range (−200 – +200)oC and frequency range (102–105) Hz. The nonmonotonic temperature dependences of dielectric permittivity of the studied composite films have a wide plateau-like maxima located between 80oС and 160oС, in contrast to the relatively sharp maximum near the Curie temperature (∼124oC) observed in the fine-grained and coarse-grained ceramics, sintered from the same nanosized or submicron BaTiO3 particles at 1250oC. The shift of the dielectric permittivity and losses maxima (in more than 40oC) and their strong frequency dispersion do not agree with the behavior expected for the systems with a weak interaction between ferroelectric particles and a polymeric matrix. In contrast, we reveal the relaxor-like behavior of the composite dielectric response. To explain the observed results, we propose the analytical model, which considers the strong dipole-dipole cross-interaction of the BaTiO3 particles in the dense nanocomposite. The analytical model is corroborated by the structural studies of the BaTiO3 nanosized and submicron particles by X-ray phase analysis and static 137Ba NMR spectra, as well as by the finite element modelling of the composite polar properties, which confirms the strong cross-interactions between the dipole moments of single-domain nanoparticles and/or between the domain walls of different submicron polydomain particles.The obtained results may be useful for development of cheap and flexible lead-free dense ferroelectric nanocomposites with relaxor-like behavior of the dielectric response, which are promising for non-volatile memory and energy-saving elements, modulators, electrical converters and piezoresistive elements.

Nickel sulfide nanoparticles decorated on carbon spheres derived from Verbena officinalis for high-performance asymmetric all-solid-state flexible supercapacitors

The crafting and development of electrode materials possessing extensive energy storage capacities, alongside their adherence to environmental and economic principles, along with their outstanding capacitive behaviors, stand as pivotal elements in propelling the technological progress of supercapacitors. In this study, we utilized discarded Verbena officinalis (VOCs) as a carbon substrate and successfully synthesized porous hollow carbon spheres through an in-situ hydrothermal method, subsequently depositing NiS nanoparticles to form a shell-like structured material. The optimized VOCs/NiS-3 composite material exhibited an exceptional specific capacitance of 202.8 mAh g−1 at a current density of 1.0 A g−1; it maintained 71 % of its capacitance even at a high current density of 10 A g−1 (144.2 mAh g−1). After enduring 10,000 charge-discharge iterations, the preservation of charge storage capacity was 81.7 %, highlighting the material's outstanding performance in terms of rapid charge-discharge rates and enduring stability. Furthermore, within a PVA/KOH gel electrolyte, we fabricated an asymmetric all-solid-state supercapacitor device that delivered an energy density of 32.58 Wh k g−1 at a power density of 800 W k g−1. The device sustained a capacitance loss rate of 9.9 % and a coulombic efficiency of 96.8 % after 5000 cycles. Even after 3000 repeated bending at 120°, the capacitance retention reached 88.3 %, indicating the device's exceptional specific capacitance, flexibility and longevity. This research offers a renewable and waste-resource recycling design strategy for synthesizing outstanding-performance, flexible, all-solid-state supercapacitor electrode materials with NiS deposited on discarded biomass carbon, unveiling considerable potential for enhancing energy storage efficiency.

High performance biochar derived from mycelium-based leather composites waste for energy storage applications

The mycelial waste generated during the production of mycelium-based leather composites presents both opportunities and challenges in maximizing biomass resource efficiency. In this study, we synthesized mesoporous biochar (AGLM-5) with a specific surface area of 3151.9 m2/g through the KOH activation method using Ganoderma lucidum mycelium waste as the precursor material. AGLM-5 exhibited exceptional performance in a three-electrode system test, demonstrating a specific capacitance of 303.5 F/g. In a two-electrode system test, it achieved an energy density of 45.5 Wh/kg at a power density of 450.7 W/kg. The symmetric supercapacitor assembled using AGLM-5 demonstrated outstanding cycling stability over 10,000 cycles, exhibiting a capacitance loss of less than 4 % throughout the entire testing period. Additionally, we employed a hydrothermal method to synthesize composite electrode sheets (δ-MnO2/AGLM-5), which not only supported the layered structure of δ-MnO2 but also significantly improved the cycling stability and electrical conductivity of aqueous zinc ion batteries (AZIB). This study presents an environmentally friendly and sustainable approach for utilizing Ganoderma lucidum mycelial biomass, with particular emphasis on the potential application of mycelial carbon materials in battery energy storage.

High energy density of biaxially oriented polypropylene film in cryogenic environment for advanced capacitor

In this paper, a method of significantly increasing the energy density of biaxially oriented polypropylene (BOPP) film by cryogenic environment has been proposed. The notable enhancements in the dielectric and energy storage performance can be attributed to precise microstructure manipulation, aimed at controlling charge injection limitations and optimizing molecular chain dynamics. The experimental results show that the maximum discharged energy density of BOPP film with thicknesses of 3.4 μwm has reached 11.83 J cm−3 at −196 °C (2.9 times that at 25 °C) with a charge-discharge efficiency of 92.74%. The direct current breakdown strength as high as 1120.4 kV mm−1 is obtained at −196 °C, exhibiting a substantial 63.7% augmentation compared to the measurement at 25 °C. Furthermore, reductions in conductance loss and capacitance loss (post self-healing testing) are realized. Mechanistic insights into the observed enhancements are investigated through computational simulations. This research provides a pivotal advancement and valuable perspective towards the development of film capacitors boasting the excellent energy storage characteristics.

Minimizing Output Capacitance Loss in GaN Power HEMT

Minimizing Output Capacitance Loss in GaN Power HEMT

Capacitance Evaluation of Metallized Polypropylene Film Capacitors Considering Cumulative Self-Healing Damage

Self-healing (SH) in metallized polypropylene film capacitors (MPPFCs) can lead to irreversible damage to electrode and dielectric structures, resulting in capacitance loss and significant stability degradation, especially under cumulative SH conditions. To enhance the reliability assessment of MPPFCs post-SH, this study conducted SH experiments on MPPFCs, examined the damage patterns of the electrodes and dielectric films, and proposed a novel capacitance evaluation method for MPPFCs under cumulative SH conditions. The results reveal that with increasing SH voltage, the number of dielectric layers experiencing single SH breakdowns rises, SH energy significantly escalates, and the loss area of the electrode due to high-temperature evaporation expands. Under cumulative SH conditions, the number of SH events is linearly correlated with the total number of SH-breakdown film layers and shows an exponential decay with the average single SH energy. By utilizing a Support Vector Machine (SVM) to classify the SH condition and damage features within the capacitor based on the correlation and distribution patterns of SH feature parameters, this study introduces an advanced method for evaluating the capacitance of MPPFCs under cumulative SH conditions. This method promises to improve the predictive maintenance and reliability of power electronic systems utilizing MPPFCs.

KHCO3 chemical-activated hydrothermal porous carbon derived from jackfruit inner skin for supercapacitor applications

The reuse of waste biomass resources had become a hot spot in the sustainable development of human society. Due to the complexity of biomass composition and microstructure, the quality reproducibility of biomass porous carbon was poor. Therefore, it was of great significance to develop a reliable method for preparing porous carbon from biomass. In this paper, a combination of hydrothermal carbonization treatment and mild activation of KHCO3 was used to prepare iron-modified porous carbon with carbon spheres/nanoplates structure, which promoted ion/electrolyte diffusion and increased the accessibility between surface area and electrolyte ions. Therefore, the active porous carbon from the Jackfruit inner skin has good specific capacitance (273.2 F/g at 1 A/g) and good cycle stability, and the capacitance loss is only 6.6 % after 10,000 charge discharge cycles. The above results showed that hydrothermal treatment and mild activation methods provided an effective way to transform waste biomass into high-performance electrode material.

Ti2TaC2: A novel out-of-plane ordered MXene towards flexible and cytocompatible supercapacitors

Exploring biocompatible and flexible supercapacitor electrode material is crucial for expanding the development of health monitoring bioelectronics. MXene films, due to their low cost, high conductivity, and excellent durability under different deformation conditions, are highly competitive in bioelectronic device applications compared with traditional carbon-based materials. Herein, a novel out-of-plane ordered double transition metal MXene (Ti2TaC2) is elaborately designed and originally synthesized, where Ti atoms preferentially reside in the outer transition metal layer and Ta atoms occupy in the middle layer. Theoretical calculations prove that the introduction of Ta species into Ti3C2 MXene enlarges the work function, raises the d-band center close to Fermi level and increases the density of states of d-orbital. Consequently, the Ti2TaC2 film delivers high specific capacitance of 313 F g−1 at 2 mV s−1 and excellent cycling stability without capacitance loss after 10,000 cycles at 10 A/g. Furthermore, the safety and cytotoxicity of Ti2TaC2 material are innovatively evaluated in vitro multiple cell lines (e.g., 293T, bEnd.3, PC-12, BV2 and HUVEC cells) and implanted into the subcutaneous tissue of mice, proving its good biosafety and cytocompatibility. The results suggest that flexible Ti2TaC2 MXene film may be a promising cytocompatible electrode material for long-term health monitoring bioelectronics.

High-performance flexible asymmetric supercapacitor utilizing hierarchical NiCo2O4 nanosheets supported on porous carbonized Verbena leaves

This study employed three-dimensional porous carbon with high surface area as the conductive substrate for composite electrode materials, aiming to facilitate rapid charge transfer and ion diffusion to increase the specific capacitance of pseudo-capacitive materials. We employed an in-situ hydrothermal method to anchor NiCo2O4 onto the porous carbonized verbena leaves, yielding nanostructured VC@NiCo2O4-8 composite electrode materials. At a current density of 1.0 A g-1, VC@NiCo2O4-8 exhibited a high specific capacitance of up to 2061.8 F g−1 and remarkable cycling stability (with only 7.8 % capacitance loss after 10000 cycles). Additionally, we assembled VC@NiCo2O4-8//VC asymmetric all-solid-state flexible supercapacitors, attaining a significant energy density of 54.0 Wh kg−1 at a power density of 695 W kg−1, while maintaining good flexibility and stability. This study provides a simple and effective method for the design and construction of high-performance electrode materials for flexible energy storage devices.

Mechanically Mixed Thermally Expanded Graphite/Cobalt(II) Perrhenate—Co(ReO4)2—As Electrodes in Hybrid Symmetric Supercapacitors

A mechanically homogenized composite of expanded graphite and cobalt(II) perrhenate has been described. Cobalt(II) perrhenate was obtained in a reaction of perrhenic acid with cobalt(II) nitrate. A simple mortar homogenization method was used to enhance the intercalation of cobalt species within the carbon matrix. The specific capacitance of the composite was enhanced by 50% (to 78 F/g) in comparison to bare expanded graphite (52 F/g). The electrochemical characteristics were significantly improved, including better cyclability (7% capacitance loss), a lower resistance of the electrode material, and a lower iR drop, with respect to expanded graphite without cobalt(II) perrhenate active species. Expanded graphite, with its unique specific surface area and pore size diameter, was proved to be a potential and cheap carbon support.

KHCO3 Chemical-Activated Hydrothermal Porous Carbon Derived from Sugarcane bagasse for Supercapacitor Applications.

The reuse of waste biomass resources had become a hot topic in the sustainable development of human society. Biomass was an ideal precursor for preparing porous carbon. However, due to the complexity of biomass composition and microstructure, the quality reproducibility of biomass porous carbon was poor. Therefore, it was of great significance to develop a reliable method for preparing porous carbon from biomass. In this paper, the activated hydrothermal porous carbon was prepared by a combination of hydrothermal carbonization treatment and KHCO3 mild activation. The hydrothermal carbonization treatment could complete the morphology adjustment and iron doping of the carbon in one step, and the mild activation of KHCO3 could activate the porous carbon while maintaining the spherical morphology. Fe-modified porous carbon with carbon ball/nanosheet structure prepared from bagasse exhibited a high surface area (2169.8 m2/g), which facilitated ion/electrolyte diffusion and increased accessibility between surface area and electrolyte ions. Therefore, bagasse derived activated porous carbon had good specific capacitance (315.2 F/g at 1 A/g) and good cycle stability, with a capacitance loss of only 5.8 % after 5000 charge-discharge cycles, and the Na2SO4-based device showed the maximum energy density of 13.02 Wh/kg. This study showed that the combination of hydrothermal treatment and mild activation provided an effective way for the conversion of waste biomass into high-performance electrode materials.

Theoretical Investigation of the Potential-Dependent CO Adsorption on Copper Electrodes.

Despite the importance of CO adsorption in many electrocatalytic reaction mechanisms, there has been little investigation of the dependence of the free energy of CO adsorption on the applied potential. Herein, we report on the potential-dependent adsorption of CO on Cu electrodes using a grand-canonical density functional theory approach. We demonstrate that, within the working potential range of electrocatalytic CO2 reduction on Cu(111) and Cu(100), the CO adsorption strength can change by over 0.1 eV. Our analyses explain the potential dependence through an interfacial capacitance loss upon CO adsorption as well as orbital relaxation induced by the electrode potential. Via sensitivity analysis with respect to two electrolyte model parameters (solvent dielectric constant and Debye screening length), we find that the surface excess charge density is a useful descriptor of the CO adsorption free energy.

Effect of Graphene Oxide Addition on the Properties of Electrochemically Synthesized Polyaniline-Graphene Oxide Films.

In this work, the electrochemical synthesis of PANI and GO-modified PANI was performed using cyclic voltammetry, varying the amount of GO, 1 mg (PG1), 5 mg (PG5), and 10 mg (PG10) to analyze the effect of the amount of GO on the composite. PANI, PG1, PG5, and PG10 materials were characterized using optical microscopy, SEM, UV-vis, FTIR, Raman, and wettability. A stability test was also carried out by putting the materials to 500 oxidation-reduction cycles using cyclic voltammetry. The synthesis method allowed GO in PANI to be added through a chemical interaction between the two compounds. It was also found that the addition of GO led to an improvement in the hydrophilic character of the composite, which would lead to an improvement in the diffusion of reagents/species when the composites are used in aqueous media processes. The results of the stability test showed that the PG10 material presented a lower % loss of specific capacitance and energy compared with the other materials, which indicates that the GO presence (in the amount specified) improves the stability of the PANI. The PG10 material showed favorable and promising conditions for its use in fuel cell and battery processes.

Fabrication of Co1.5Ni1.5S4 and Prussian blue analogues composites with yolk-shell heterostructures as cathode and biomass derived carbon as anode for asymmetric supercapacitors

As highly efficient electrode materials for supercapacitors, the clean production of transition metal sulfide and biomass-derived carbon played an important role in promoting the practical process. In this work, Prussian blue analogues were grown in situ on glycerate precursors through a simple ion-exchange process, followed by sulfidation to obtain the Co1.5Ni1.5S4 and Prussian blue analogues composite microspheres with yolk-shell structures. Thanks to the unique micro-nano structure and multi-element synergy, composites exhibited excellent specific capacitance (up to 2388.7 F g−1 at 1 A g−1), rate performance (55.0 % capacitance retention at 30 A g−1), and cycling stability (capacitance maintained at 81.5 % after 5000 cycles). In addition, Nitrogen-doped sunflower seed shell derived carbon, prepared by two pyrolysis and salt-activation processes, could attain a specific capacitance of 347.1 F g−1 at 1 A g−1 and an almost undiminished capacity of 5000 cycles. With Co1.5Ni1.5S4 and Prussian blue analogues composites as cathode and derived carbon as anode, the assembled hybrid supercapacitor exhibited an eminent energy density of 82.2 Wh kg−1 (at a power density of 904.9 W kg−1) and stable cycling characteristics (only 16.7 % loss of capacitance after 10,000 cycles). This work provided a feasible scheme for the structure regulation of sulfides and the defect construction of porous carbon.

FeCl3-modified carbon as an electrode material for supercapacitors: preparation, analysis, and electrochemical properties

The necessity to combat the effects of global warming has made the use of renewable energy sources essential. Much attention has been focused on utilizing various types of biomass that can provide high energy productivity and serve as an alternative to traditional fossil fuels. This study specifically aims to investigate the electrochemical properties of carbon materials obtained from plant-based raw materials after biofuel production by the carbonization of melon and citrus peels at 300 °C and chemical activation using FeCl3. It is established that chemical activation with FeCl3 at 700 °C has led to dehydration, degradation of the carbon matrix, and the development of a microporous surface. For a two-electrode electrochemical cell, the specific capacitance values at a discharge current of 50 mA are 196 F/g in an aqueous KOH solution and 78 F/g in TEABF4. Based on the impedance spectroscopy results, an equivalent electrical circuit has been modeled, revealing the energy storage mechanism at the carbon electrode-electrolyte interface, with a physical interpretation of each circuit element provided. Most importantly, the device remains stable with no capacitance loss after 1000 cycles. The research findings may contribute to expanding the use of biomass as a cost-effective electrode component for supercapacitors.