Low Equivalent Series Resistance Research Articles

Coal-based graphene formation by CO2 laser scribing: Various structures and excellent electrochemical performance

The laser-induced technique is a cost-effective and environmentally-friendly method for upgrading coal into high value-added graphene materials. Here, laser-induced graphenes (LIGs) were prepared from different rank coals in one-step under vacuum conditions using a designed CO2 infrared laser device. The characteristics of laser-induced products were studied by X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy, scanning electron microscopy, and high-resolution transmission electron microscopy. The electrochemical characteristics of coal-based laser-induced graphenes (C-LIGs) were examined in a three-electrode test system. Results show that subbituminous coal, bituminous coal, and low-metamorphic anthracite can form LIG with fewer layers after laser irradiation. The morphology of C-LIG is a layered porous structure. Corrugated folds can be observed at the edges of the C-LIG layer. There are only a few layers of graphene, with the majority of them concentrated in 2–10 layers. The most interesting result is that LIG prepared from low volatile bituminous coal has the highest crystallinity, the largest aromatic layer size, and the lowest average graphene layer number. Furthermore, LIG made from low volatile bituminous coal (LIG-ZJ) exhibits excellent electrical double-layer capacitive behavior, low equivalent series resistance (3.73 Ω), good rate capability, excellent cycling stability, greater Coulombic efficiency, and high mass specific capacitance. The LIG-ZJ electrode exhibits a high specific capacitance of 1879.92 F/g at 1 A/g, which is nearly ten times greater than that of most activated carbon electrodes reported. In addition, its power density and energy density can reach up to 924.07 kW/kg and 217.11 Wh/kg. These results indicate that coal-based laser-induced graphene has significant potential for application in the field of electrochemical energy storage.

An appraisal of the role of lanthanide doping in stabilization and performance improvement of [Sm3+-Eu3+-Tm3+]:CsPbI2.2Br0.8 for high-performance energy systems

Energy sustainability in the present era is associated with the adoption of the integrated and consolidated approach to generate, convert, and store energy. Current investigation is demonstrative of the first exploration of the novel CsPbI2.2Br0.8 transformed by lanthanide triple doping forming [Sm3+-Eu3+-Tm3+]:CsPbI2.2Br0.8 (SET:CPVSK). Also, SET:CPVSK is the for the first time employed in multitudinous energy applications. SET:CPVSK excelled over the pristine material with the minimal alterations in the band gap energy spanning around 1.65 – 1.72 eV tracked for 28 days. With the cubic phase, SET:CPVSK thin films exhibited excellent morphology with the tighter binding to substrate. As light harvesting layers inside entirely ambient perovskite solar cells, the efficiency of the cells increased to 16.31 % from 7.49 % upon doping with an improvement in other photovoltaic features also. Electro-catalytic response of the SET:CPVSK towards hydrogen generation was magnanimous with the lower overpotential and kinetic Tafel slope of 130 mV and 116.5 mV dec−1, signifying Volmer-Heyrovsky mechanistic route. With the service life of 100 min, the developed electro-catalyst expressed sustainable output. In terms of the charge storage, the unit capacity was improved to 622.4 mAH g−1 upon doping while the other electrode can only reach up to 394.2 mAH g−1. Furthermore, the resistive response of this electrode was also appreciable with the lower equivalent series resistance (Rs) i.e. 0.41 Ω, showing auspiciousness for practical applications.

Challenges in Measurement of Low-Value ESL and ESR of High-Performance PFN Capacitors for Klystron Modulator

In the high voltage line type pulse modulators, Pulse Forming Network (PFN) capacitors are one of the important components. These capacitors operate at peak kilo ampere current range and at repetition rate in the range of a few hundred hertz. The performance of these capacitors is critical w.r.t. overall system performance, and they are required to operate at high power density and low losses with high reliability. The Equivalent Series Inductance (ESL) and Equivalent Series Resistance (ESR) are two critical parameters that affect the performance of these capacitors. PFN modulator demands a capacitor of very low ESL and ESR for reliable operation and generation of high-voltage pulses. Higher ESR value adversely affects the performance of the capacitor by raising its temperature and thus deteriorating its life. ESL value does not directly affect life, but it affects the quality of high voltage pulse. In RRCAT, the PFN capacitors purchased from Indian manufacturers were showing high-temperature rise and failures. Therefore, new capacitors were designed to have lower ESL and ESR values. Measurement of ESL and ESR is important to evaluate the performance of the capacitors. The low value of these parameters makes their measurement a challenging task and requires special techniques. For low values of ESL and ESR (less than 100 mΩ) measurement, a differential measurement technique was used in which modification and different layouts were explored to improve the repetitive accuracy of the measurements. The differential ESR and ESL measurement techniques with more emphasis on the low-value ESR measurement will be discussed in the paper.

Oxygen vacancy enhancing intrinsic conductivity of rGO@MnO2−x electrode for efficient hybrid capacitive deionization

The poor intrinsic conductivity and serious aggregation of MnO2 has limited its further application in capacitive deionization (CDI). In the present work, GO was introduced as the growth substrate to alleviate the aggregation behavior of MnO2, while oxygen vacancies were created in the MnO2 crystal by calcination to improve the intrinsic conductivity of MnO2. The uniform dispersion and the expanded layer spacing of δ-MnO2 provide larger specific surface area and more active sites for ion adsorption and storage, while the abundant oxygen vacancies in the crystal enhance the intrinsic conductivity and provide convenient ion transport channels for ion movement and transport. The electrochemical tests show that the rGO@MnO2−x electrode presents higher specific capacitance (284 F g−1) and lower equivalent series resistance (1.11 Ω) than those of MnO2 electrode (128 F g−1 and 1.25 Ω). Meanwhile, the desalination tests display that the hybrid GO||rGO@MnO2−x cell demonstrates prominent desalination capacity (58.75 mg g−1) and ultrahigh charge efficiency (95.01%) compared to GO||MnO2 cell (38.25 mg g−1 and 83.81%) in 500 mg L−1 NaCl solution at 1.2 V. The proposed design offers an optional strategy to improve the intrinsic conductivity of MnO2 and enables synthesis of a novel composite to achieve efficient desalination.

A comprehensive study on effect of carbon nanomaterials as conductive additives in EDLCs

This study performs a comprehensive investigation to objectively analyze the effects of various carbon nanomaterials using as conductive additives (5 wt%) in activated carbon (AC) based electrodes for electrical double-layer capacitors (EDLCs). A variety of carbon nanomaterials including carbon black (CB), single-walled carbon nanotubes (SWCNT), graphene nanoplatelets (GNP), fullerenes (C60), and activated carbon nanofibers (ACNF) are considered in this work as they provide a diverse combination of intrinsic properties such as specific surface area, conductivity, micro-mesoporous structures, and geometry of nanomaterials. These additives are incorporated into freestanding carbon electrodes, and their EDLC performance in a neutral aqueous electrolyte is investigated by means of electrochemical measurements. The findings from this work provide useful insight into how the properties of various carbon nanomaterials influence EDLC performance in different aspects such as capacitive behavior, resistivity, performance at different current densities, charge propagation properties, and stability over long-term cycling. The results show that each carbon additive has its own strengths and limitations for different performance parameters considered. The unfavorable material properties of C60 cause a significant decrease in capacitance at high current density, leading to the lowest device performance incorporated with C60 as additives. While GNP and SWCNT show high crystallinity, low ID/IG ratios, the EDLCs still exhibit decreased specific capacitance and moderate energy densities due to their relatively limited specific surface area and high resistivity of the resultant composite electrodes compared to the pristine AC. The CB additives-based samples demonstrate the highest conductivity of dry electrodes and low equivalent series resistance (ESR) in EDLCs. On the other hand, a reduction in capacitance at high current densities and material degradation during long-term cycling are observed for CB samples, which could be attributed to the high dispersibility of CB causing limited interparticle voids and thus increasing diffusion resistance. In contrast, the use of ACNFs significantly reduces the diffusion resistance and improves the cyclic stability compared with CB based samples due to the advantages of larger specific surface area and superior micro-mesoporous structures of ACNFs. In particular, EDLCs with ACNFs demonstrate an increase in specific capacitance and energy density by 99 % and 76 %, respectively compared to CB based EDLCs at a current density of 20 A/g. This work elucidates the complex interplay between carbon nanomaterials using as additives and corresponding EDLC performance. These results provide important information to the community for future development of new energy conversion and storage devices.

Sm-Eu-Tm]:CsPbI2Br1 perovskite hetero-system: Probing rare earth driven stabilization for sustainable energy conversion, generation, and storage capacity

This is the first report on the lanthanide doped cesium lead halide perovskite using triple doping mechanism for formation of the novel [Sm-Eu-Tm]:CsPbI2Br1 perovskite (SET-CPVSK) hetero-structure. SET-CPVSK remained intact in terms of opto-electronic response shown by slight alleviation in band gap from 1.63 to 1.66 eV for 28 days. It attained the characteristic black cubic phase (ABX3 crystalline orientation) when thermally treated at 200 °C. The deposited thin films were smoother and devoid of any pinholes. Planar and ambient perovskite solar cell containing SET-CPVSK absorber was 14.06 % efficient. This solar cell was also hysteresis free with 63.14 % fill factor. The profound electro-catalytic output towards O2 and H2 generation achieved with the SET-CPVSK was reflected by the lower overpotential values of 50 and 140 mV, respectively. The kinetic favorability was also disclosed by lower Tafel slope values. As a potential energy storage material, SET-CPVSK adorned electrode achieved the unit capacity of 554.4 mA H g−1 with the impressively lower equivalent series resistance (Rs) of 0.79 Ω depicting lower impedance and subsequently higher diffusion of the ions. SET-CPVSK is a sustainable energy material which has the potential to replace potentially expensive materials due to its impressive efficiency and stability.

Capacitor for the voltage-surge suppression in a SiC-MOSFET half-bridge inverter

This paper explores some efforts to suppress the voltage surge appearing during the operation of a SiC-MOSFET-based half-bridge circuit in an inverter topology. The study is important to carry out, as the voltage surge problem does not come up when a Si-IGBT is used as the switching component in the half-bridge; however, some applications demand certain properties like what is found in a SiC MOSFET. Compared to Si-IGBT with rise-time/fall-time larger than 100 ns in general, the use of SiC MOSFET is preferable due to its much shorter switching time, less than 50 ns, which brings about a much lower switching loss and lower operating temperature. However, the choice of the usual electrolytic capacitor in the dc-link would produce an undesired voltage surge during the half-bridge operation. The origin of the surge is sometimes assigned to the inductance parasitic effect of the SiC-MOSFET high frequency. This research proves the benefit of a film capacitor to suppress the surge due to its lower equivalent series resistance (ESR) than that of the electrolytic capacitor. The results contribute to the consideration to take during the circuit realization in various applications, as there are not many papers yet found discussing the use of film capacitor in the dc-link of a SiC-MOSFET half-bridge inverter. This study also reveals the importance of the film capacitor placement during the design stage of SiC-MOSFET applications; moreover, motor controllers being equipped with an inverter such as described in this study have not been found yet in the market. The efforts investigated in this work would help to control the undesirable voltage spikes that frequently occur when applying a SiC-MOSFET to a half-bridge inverter design

HKUST-1 as a Positive Electrode Material for Supercapattery

The copper-based metal-organic framework (HKUST-1) exhibits interesting properties, such as high porosity and large specific surface area, which are useful as electrode materials for supercapattery. Herein, the HKUST-1 was synthesized through a facile hydrothermal method and exhibited a typical octahedral structure with a specific surface area of 1015.02 m2 g−1, which was calculated using the Barrett–Joyner–Halenda (BJH) method. From the three-electrode analysis, the HKUST-1 demonstrated a specific capacity of 126.2 C g−1 in 1 M LiOH. The structural fingerprint of the HKUST-1 was confirmed with Fourier-transform infrared spectroscopy, Raman spectroscopy, and X-ray diffraction spectroscopy. A supercapattery device, i.e., the HKUST-1//N-doped graphene, revealed a maximum specific power of 300 W kg−1 and a specific energy of 2.61 W h kg−1 at 1 A g−1 with 57% capacitance retention during continuous charging–discharging, even after 10,000 cycles. The HKUST-1 also demonstrated a low charge transfer resistance and a low equivalent series resistance of 7.86 Ω and 0.87 Ω, respectively, verifying its good conductivity. The prominent supercapattery performance of the HKUST-1//N-doped graphene suggested that the HKUST-1 is a promising positive electrode for supercapattery.

Intriguing and Facile Preparation Approach of CdO Nanorod-Based Abundant Chitosan for Symmetric Supercapacitors.

Abundant chitosan was rationally used for the green fabrication of cadmium oxide nanorods (CdO nanorods) owing to its environmentally benign characteristics, bioavailability, low cost, etc. However, the primary unsubstituted amino group of chitosan interacts with the surface of Cd salt at higher temperatures, resulting in CdO nanorod formation. A one-step hydrothermal technique was adopted in the presence of chitosan. Optical, structural, and morphology techniques characterized CdO nanorods. According to X-ray diffraction crystallography, CdO is well crystallized in the face-centered cubic lattice with an Fm-3m (225) space group. The AC@CdO nanoelectrode demonstrated an outstanding gravimetric capacitance of 320 F g-1 at a current density of 0.5 A g-1, nearly three-fold that of ordinary AC electrodes. The AC electrode and the AC@CdO nanoelectrode retain 90 and 93% of their initial specific capacitance after 10,000 galvanostatic charge discharge cycles. The AC@CdO nanoelectrode has a lower equivalent series resistance value than the AC electrode. Moreover, AC@CdO symmetric supercapacitor devices achieve excellent results in terms of specific energy, specific power, and capacitance retention.

Iron Selenide Particles for High-Performance Supercapacitors.

Nowadays, iron (II) selenide (FeSe), which has been widely studied for years to unveil the high-temperature superconductivity in iron-based superconductors, is drawing increasing attention in the electrical energy storage (EES) field as a supercapacitor electrode because of its many advantages. In this study, very small FeSe particles were synthesized via a simple, low-cost, easily scalable, and reproducible solvothermal method. The FeSe particles were characterized using cyclic voltammetry (CV), galvanostatic charge/discharge (GCD) measurements, and electrochemical impedance spectroscopy (EIS), revealing enhanced electrochemical properties: a high capacitance of 280 F/g at 0.5 A/g, a rather high energy density of 39 Wh/kg and a corresponding power density of 306 W/kg at 0.5 A/g, an extremely high cycling stability (capacitance retention of 92% after 30,000 cycles at 1 A/g), and a rather low equivalent series resistance (RESR) of ~2 Ω.

Wet-chemical engineering of Ag-BiVO4/Bi2S3 heterostructured nanocomposite on graphitic carbon nitride (g-C3N4) sheets for high performance supercapacitor application

Graphitic carbon nitride (g-C3N4), a structural analogue of graphite has opened a new arena in energy storage. The N-rich g-C3N4 sheets similar to N-doped carbon materials provide large number of defect sites for increased diffusion and adsorption of electrolyte ions. High N-content in g-C3N4 is most suitable to escalate metal‑carbon binding energy which stabilizes the pseudo-active transition metal oxides/chalcogenides over carbon support to realize high capacitive performance. In this study, we have impregnated binary Ag-BiVO4/Bi2S3 heterostructures on g-C3N4 sheets through wet-chemical approach, as novel electrode material for supercapacitor application. As prepared Ag-BiVO4/Bi2S3@g-C3N4 composite (ABVBS@g-C3N4) along with Ag-BiVO4/Bi2S3 (ABVBS), Ag-BiVO4 (ABV), and Bi2S3 (BS) were systematically characterized by different techniques i.e., XRD, FTIR, FESEM, EDS, and BET analysis. When applied for electrochemical tests, among all the analyzed electrodes ternary composite ABVBS@g-C3N4 exhibited highest electrochemical activity with a specific capacitance value of 872 F/g (@5 mV/s) and 815.4 F/g (@1 A/g), and 91.5 % capacitance retention up to 5000 GCD cycles. The initial coulombic efficiency of ABVBS@g-C3N4 was noteworthy (99.42 %) due to very low internal resistance. Moreover, it was analyzed that ternary composite ABVBS@g-C3N4 has lower equivalent series resistance (RES) as 6.73 Ω and charge transfer resistance value as 7.73 Ω, in comparison to other electrodes. This excellent electrochemical performance of ABVBS@g-C3N4 is attributed to combined contributions from ABVBS and g-C3N4 in terms of multiple redox states, increased wettability of electrode, and high structural and chemical stability. Considering the results, our study proposes feasible strategy to generate hybrid electrode materials with optimized properties to serve as energy storage material for next generation supercapacitors.

Oil palm lignin-derived laser scribed graphene in neutral electrolyte for high-performance microsupercapacitor application

Lignin is a renewable natural resource that could be derived from oil palm empty fruit bunches. It has generated significant interest as a precursor in synthesizing graphene as anode and cathode material for supercapacitors. In this paper, we report the synthesis of 3D hierarchical Laser Scribed Graphene (LSG) on a flexible polyimide substrate from lignin extracted from empty fruit bunches (EFB) of oil palm for microsupercapacitor applications. The intensity and speed of the laser have been tuned to yield densely compacted oil palm lignin LSG at a laser power of 70% and a speed of 30% (OPL-LSG 7030). OPL-LSG 7030 possessed lower equivalent series resistance of 60.1 Ω and a larger crystalline size of ∼31 nm than the rest of the tested samples. It exhibited exceptional areal capacitance of 30.77 mFcm−2 at a current density of 0.08 mAcm−2, an energy density of 0.00176 mWhcm−2 and a power density of 0.25 mWcm−2 when using a unique neutral PAAS/K2SO4 gel electrolyte. It achieved excellent capacitance retention of 88.4% after 5000 charge/discharge cycles and remarkable mechanical stability of 95% after 400 bending cycles. Furthermore, electrochemical studies revealed the redox properties of readily available quinone/ hydroquinone in the oil palm lignin, which could be inherited in graphene electrodes through a feasible and affordable approach for flexible green energy storage applications.

Structure and Electric Properties of Anodized Aluminum with PEDOT:PSS Conductive Polymer Cathode

Aluminum solid electrolytic capacitors using a conductive polymer as a cathode material has the advantages of low equivalent series resistance (ESR) and high thermal stability compared to aluminum electrolytic capacitors using liquid electrolytes. A disadvantage of aluminum solid electrolytic capacitors with a conductive polymer is the low breakdown voltages, limiting the operating voltage of the capacitors to ∼100 V or less. In this study, for a possible future increment of the withstand voltages of solid electrolytic capacitors, PEDOT:PSS-coated aluminum with an amorphous or crystalline alumina layer formed at 500 V has been characterized using SEM, STEM/EDS, and conductive AFM to understand the distribution of PEDOT:PSS conductive polymer and its influence on the electric properties. The crystalline alumina layer, developed beneath a porous hydrated alumina layer, contains many voids, which increase the leakage current compared to the void-less amorphous alumina layer. However, the crystalline alumina layer with PEDOT:PSS exhibits a higher breakdown voltage than the amorphous one. The limited incorporation of PEDOT:PSS into the inner part of the porous hydrated alumina layer may introduce a resistive surface layer, possibly contributing to the increased dielectric breakdown.

Capillary Evaporation on High-Dense Conductive Ramie Carbon for Assisting Highly Volumetric-Performance Supercapacitors.

Conductive biomass carbon possesses unique properties of excellent conductivity andoutstanding thermal stability, which can be widely used as conductive additive. However, building the high-dense conductive biomass carbon with highly graphitized microcrystals at a lower carbonization temperature is still a major challenge because of structural disorder and low crystallinity of source material. Herein, a simple capillary evaporation method to efficiently build the high-dense conductive ramie carbon (hd-CRC) with the higher tap density of 0.47 cm3 g-1 than commercialized Super-C45 (0.16 cm3 g-1 ) is reported. Such highly graphitized microcrystals of hd-CRC can achieve the high electrical conductivity of 94.55 S cm-1 at the yield strength of 92.04MPa , which is higher than commercialized Super-C45 (83.92 S cm-1 at 92.04MPa). As a demonstration, hd-CRC based symmetrical supercapacitors possess a highly volumetric energy density of 9.01Wh L-1 at 25.87kW L-1 , much more than those of commercialized Super-C45 (5.06Wh L-1 and 19.30kW L-1 ). Remarkably, the flexible package supercapacitor remarkably presents a low leakage current of 10.27mA and low equivalent series resistance of 3.93 mΩ. Evidently, this work is a meaningful step toward high-dense conductive biomass carbon from traditional biomass graphite carbon, greatly promoting the highly-volumetric-performance supercapacitors.

Investigation of charge storage in admixture of dextrose derived interconnected carbon spheres and micro-sized silicon

This work reports the investigations and electrochemical properties of a material, prepared by micro-sized Si (mSi) (upto 50 μm) which were partially coated with upto ~7 μm sized carbon microspheres (CS). The mixture of mSi enwrapped with CS ([email protected]) was fabricated using a low temperature and facile hydrothermal carbonization (HTC) of dextrose. XRD and Raman study revealed an amorphous phase due to carbon/SiO2 and a highly disordered nanocrystalline graphite respectively. Also, FTIR suggested the SiO bending and symmetric stretching of linear SiOSi. The electrochemical investigation with three cell assembly of fabricated [email protected] as an electrode material for supercapacitor application exhibited a maximum specific capacitance of 278.79 F g−1 at 5 mV s−1 scan rate which is around 7 times as calculated for pristine mSi powder. In [email protected], conducting, amorphous and nano crystalline carbon combined with mSi exhibited enhanced specific capacitance and a low equivalent series resistance (ESR). mSi served as anchor and contributed to enhancing specific capacitance and providing 2 V voltage window. This work opens the possibility of designing energy materials with the waste Si and pseudocapacitive materials.

Investigation of CuxS-based electrode for one-dimensional flexible supercapacitors and its electrochemical performances

In this study, CuxS nanoplates are in-situ synthesized on the surface of copper wire (CW) as active materials (CW@CuxS) for supercapacitor electrodes, in which CW and Na2S are respectively used as copper and sulphur sources. The CW@CuxS electrode exhibits high specific capacitance up to 3.06 F cm−3, good cycling stability with nearly 80% capacitance retention after 5000 cycles, small charge transfer resistance, and low equivalent series resistance. In addition, the CW@CuxS electrode shows excellent flexibility applied to one-dimensional supercapacitors, as indicated by the relative stability of the specific capacitance in different bending states.

Electrochemical performance of aqueous electrolytes in porous carbon derived cassava peel electrode material-based for sustainable symmetrical supercapacitor

Electrolytes have been generally recognized as one of the most important components in enhancing the electrochemical performance of supercapacitors. On the other hand, aqueous electrolytes are considered prime candidates for the development of the next generation of symmetric supercapacitors due to their low-cost, environmentally friendly, high ionic conductivity, fine ionic size, and high capacitance. Herein, the symmetrical supercapacitor of the sustainable porous carbon-based electrode material was confirmed through various aqueous electrolytes consisting of neutral, basic, and acidic Na2SO4, KOH, and H2SO4. Activated carbon is obtained from high potential biomass sources of cassava peel waste. Activated carbon synthesis was performed with a comprehensive approach in order to obtain abundant pore structure, high porosity, and improved wettability through a combination of high-temperature chemical and physical activation. in addition, the electrode material is designed to resemble a solid disc without the addition of a synthetic binder. The evaluation of the disc dimensions showed high porosity in the obtained activated carbon. Furthermore, the symmetrical supercapacitor of the optimized electrode material exhibit excellent specific capacitances of 112, 150, and 183 F g-1 at 1 mV s-1 in the electrolytes Na2SO4, KOH, and H2SO4, respectively. In addition, the highest rate capability of 70% was confirmed in the H2SO4 acid electrolyte. Moreover, their coulombic efficiency can be maintained around 89% with low equivalent series resistance 0.21-0.42 ?. Therefore, the activated carbon-based supercapacitor symmetric cell device from cassava peel shows high performance for developing high-performance supercapacitor applications with guaranteed stability in aqueous electrolytes.

One-step strategy of 3D hierarchical porous carbon with self-heteroatom-doped derived bread waste for high-performance supercapacitor

Bio-waste is a promising carbon source that can be used as a basic component in renewable supercapacitors due to its abundant hierarchical pore structure potential, heteroatom self-doping capability, high surface area, as well as well-defined chemical and mechanical stability. This study converted bread bio-waste into rich 3D hierarchical porous carbon through a one-step facile strategy to be used as the main component of a supercapacitor. The porous carbon was obtained through physical activation approach at different temperatures of 750, 800, 850, and 900 °C without being combined with chemical activation. The optimized activated carbon illustrated high porosity behavior with an abundant 3D hierarchical pore structure consisting of 76.98% micropores and 23.02% mesopores and also produced a well-defined wettability of self-doping heteroatoms. Moreover, the electrochemical behavior in a symmetric supercapacitor cell showed a high specific capacitance of 202 F g−1 at 1 A g−1 with a rate capability of 73% at 10 mV s−1 in a 1 M H2SO4 electrolyte. It was also discovered that the activation temperature of 850 produced the highest energy density of 11.61 Wh kg−1 at a power density of 156.71 W kg−1 with a low equivalent series resistance of 0.11 Ω. Finally, the proof-of-concept showed that bread waste has immense potential as a 3D hierarchical porous carbon source after the synthesis through a single-stage facile approach and can be used as a major renewable electrode component for sustainable supercapacitors.

The impact of DC-bus impedance on the switching performance of low-voltage silicon power MOSFETs

Typical DC-bus stabilization for low-voltage power circuits consists primarily of ceramic capacitors due to the capacity density and low equivalent series resistance (ESR) resulting in low conduction losses. Particularly in hard-switching and hard-commutation operation, the low ESR and high equivalent series inductance (ESL) of the capacitors in the commutation path restrict the damping of the switch node voltage overshoot and introduce high-frequency ringing, reducing the voltage margin of the transistor. Therefore, this paper analyzes the impact of the DC-bus impedance and proposes a DC-bus snubber based on an RC network to form the DC-bus impedance’s characteristic, which minimizes the overshoot voltage. A comprehensive simulation using measurement-derived component models is shown, which is verified by an in-situ measurement on a test PCB. Furthermore, transient measurements using a double pulse test setup show the effectiveness of the proposed approach.

Novel macaroni‐sponge‐like pore structure biomass (Zingiber officinale Rosc. leaves)‐based electrode material for excellent energy gravimetric supercapacitor

AbstractBACKGROUNDBiomass‐based porous carbon as the basic component of electrodes has received wide interest as a renewable energy storage device with high chemical–physical stability and environmental friendliness. Therefore, novel biomass waste based on Zingiber officinale Rosc./red ginger leaves was synthesized as an electrode‐based carbon material with an abundance of unique macaroni‐sponge‐like hierarchical pore structure, as well as good chemical, physical and economic performance. Template/metal–organic framework‐free red ginger leaf‐based hierarchical porous carbon (RGPC) was prepared using a facile and zero‐residue technique as electrode material for supercapacitor application.RESULTSAdditionally, ZnCl2 impregnation with concentrations of 0.1, 0.3 and 0.5 mol L−1 was utilized for increasing the active sites between electrode and electrolyte ions through interconnecting microchannels. The combination of macaroni‐sponge‐like structure, amorphous nature, optimum specific surface area and availability of oxygen functional groups as a self‐doping heteroatom of RGPC‐0.3 greatly optimized the electrochemical performance of symmetric supercapacitor cells. The RGPC‐0.3 electrode had an ideal specific capacitance of 215.76 F g−1 with a specific energy of 29.966 Wh kg−1 and maximum specific power of 108 W kg−1 at 1 mV s−1 in a symmetric supercapacitor system. Furthermore, a relatively good coulombic efficiency of 71.01% was obtained with a low equivalent series resistance of 0.098 Ω.CONCLUSIONSThis study provides insight into the generation of unique hierarchical porous carbon as a basic component of electrodes for energy storage applications with high electrochemical performance through the utilization of waste red ginger biomass with a simple, facile and cost‐effective strategy. © 2022 Society of Chemical Industry (SCI).