Charge-discharge Time Research Articles

Pemanfaatan Limbah Ban Bekas untuk Sintesis Nanokomposit MnO2/C dengan Metode Hidrotermal sebagai Material Superkapasitor

Activated carbon from waste tires is used as MnO2 metal oxide doping in making MnO2/C-based nanocomposites into high-density and environmentally friendly supercapacitor electrodes. The MnO2/C nanocomposite synthesis process was carried out using the hydrothermal method by varying the mass of activated carbon by 1.25 g, 2.5 g and 3.75 g to determine the optimum results. Based on the results of research that has been carried out, it shows that MnO2/C can be used as a high density supercapacitor electrode. This is in accordance with the XRD test results which show that the MnO2 nanocomposite with the addition of C was successfully synthesized and has an orthorhombic crystalline phase. The SEM test results show that the material has almost the same morphology, namely many protrusions which make each particle have high roughness. The most optimal results were obtained from the MnO2/C-50 variation because it has the highest C element content, namely 39.93%, so it has the highest capacitance value of 5.791 f/g during the CV test. The GCD test shows that electrodes with a carbon variation of 2.5 g have a much longer and constant charge-discharge measurement time. In the EIS test, this variation shows a resistance value that is not too high and not too small, materials that have good storage capacity or capacity have moderate resistance.

Moisture-Stable CsSnBr2Cl Halide Perovskite: Electrochemical Insights in Aqueous Environments.

In this investigation, moisture-stable CsSnBr2Cl nanoparticles were synthesized by incorporating Cl into CsSnBr3 halide perovskite using the hot injection method. Various analyses including XRD, XPS, UV-vis absorbance, photoluminescence, and Mott-Schottky have confirmed that the structural properties, chemical states, optical properties, and electronic band structure of CsSnBr2Cl nanoparticles remain intact even after 75 days of water immersion, thereby conclusively demonstrating their moisture stability. In a three-electrode system, the comparative electrochemical performance of pristine CsSnBr3 nanoparticles and moisture-stable Cl-incorporated CsSnBr2Cl nanoparticles was evaluated in various aqueous electrolytes, including HCl, Na2SO4, and KOH. The results indicate that the CsSnBr2Cl electrode material exhibits superior electrochemical properties, such as a larger integrated cyclic voltammetry (CV) area, a wider potential window, longer charge-discharge times, and lower impedance parameters compared to the pristine CsSnBr3 nanoparticles. The electrochemical performance of CsSnBr2Cl nanoparticles was evaluated for potential applications in batteries, supercapacitors, fuel cells, and water splitting, with a focus on reaction kinetics, charge storage mechanisms, and impedance parameters. The electrochemical properties of the nanoparticles were assessed using a three-electrode configuration across various 0.5 M aqueous electrolytes (HCl, Na2SO4, and KOH). In HCl, the nanoparticles demonstrated impressive charge storage capability, achieving a capacitance of 474 F g-1 at 1 A g-1, affirming their suitability for energy storage devices. In Na2SO4(aq.), the nanoparticles exhibited excellent stability for supercapacitors, operating up to 1.6 V without significant oxygen evolution. Notably, in KOH, they demonstrated potential as effective water-splitting electrodes. The practical applicability of the nanoparticles was evaluated using a symmetric two-electrode configuration with HCl and Na2SO4 electrolytes. The capacitance values were 117 F g-1 in HCl and 70 F g-1 in Na2SO4 at 1 A g-1. Notably, after 5000 GCD cycles in HCl(aq.), the nanoparticles retained 93% of their capacitance and maintained 91% Coulombic efficiency. They also demonstrated stable operation across a temperature range of 3 to 60 °C, achieving an energy density of 5.83 W h kg-1 at a power density of 600 W kg-1. This study emphasizes the considerable potential of CsSnBr2Cl nanoparticles in advancing electrochemical energy storage technologies and sets a solid foundation for future research and development in metal halide perovskites.

Hydrophilic porous activated biochar with high specific surface area for efficient capacitive deionization

Porous carbon electrode materials were prepared by carbonization and alkali activation from three natural porous biomasses, lotus petiole (LP), sunflower plate (SP), and lotus seedpod (LS). The pore structure, surface characteristics, and electrochemical properties of the three activated biochars were investigated and related to their CDI performance. The results indicated that the three activated biochars were hydrophilic and negatively charged, with a high specific surface area and an abundance of micropores. Due to the best surface wettability, highest specific capacitance, and shortest charge-discharge time, lotus petiole-based activated biochar (LPCK) had the highest electrosorption capacity of 8.67 mg·g−1 and faster desalination rate of 0.24 mg·g−1·min−1. Cyclic voltammetry and adsorption kinetics results indicate that the double-layer electrostatic adsorption mechanism dominated the CDI processes of the three activated biochars. The use of three biomass wastes provides low-cost, eco-friendly, and sustainable materials for the development of CDI electrodes.

Streamlined electrochemical harvesting of cobalt and nickel from soft cemented carbide scrap for superior supercapacitors

We propose a complete circular economy and sustainability model from soft cemented carbide scrap to supercapacitor application. An enhanced recovery of cobalt and nickel was observed when deep eutectic solvent was used. A comparative in-situ electrochemical deposition of the recovered metals was done on stainless steel (SS), SS/activated carbon (AC), and SS/AC/polyaniline (PANI). The optimization of electrochemical extraction was carried out by varying voltage, time, and temperature. The surface area and conductive polymer's electronic distribution contributed to different surface morphological deposition of specific metals on them. Unique fluffy particle deposition was observed on the surface as fine grain particles with uniform particle size within 1 µm. The fabricated supercapacitors showed the pseudocapacitance behaviour. The presence of metal oxide nanocomposite deposition as the active material is particularly pronounced in the SS/AC/PANI device due to the inclusion of PANI as an active material and its substantial contribution to pseudocapacitance. The higher charge-discharge time of SS/AC/PANI at the same current densities compared to SS/AC may be due to the above-mentioned additional contribution of PANI's quickly reversible redox behavior. Hence, the overall electrochemical extraction from scrap to supercapacitor will undoubtedly lead to achieving the sustainable development goals (SDGs)

Optimization of cobalt-based MOFs for super-capacitor electrode materials of new energy vehicle

Super-capacitors (SCs), as new energy conversion storage elements, have attracted much attention, but there is still a research gap in the design of electrode materials. In this study, the optimization scheme of Metal-Organic Frameworks (MOFs) and cobalt-based MOF composites as electrode materials for SCs in new energy vehicles is explored, and a series of experiments are conducted to evaluate their performance. Scanning Electron Microscope (SEM) images reveal that the cobalt-based MOF composites have a surface morphology of particles with uniform distribution. The electrochemical performance test results show that the specific capacitance of the cobalt-based MOF composites is much higher than the sum of the two individual electrode materials and presents a remarkable increase with the scanning rate. Additionally, in the constant current charge-discharge test, cobalt-based MOF composites exhibit the longest charge-discharge time and good symmetry. Electrolyte particle contact tests for samples at different preparation temperatures display that high-temperature samples have better structural stability and electrolyte ion contact. In Cyclic Voltammetry (CV) and Galvanostatic Charge Discharge (GCD) tests, the 250 °C sample demonstrates the best electrochemical properties and the highest specific capacitance (269 F/g). Moreover, as the current density increases, the specific capacitance of the 600 °C sample decreases at a lower rate, showing stronger stability. However, the use of cobalt-based MOF materials may pose environmental and safety risks, such as the environmental impact of cobalt resource mining, instability under high-temperature conditions, and the possible production of hazardous substances. Therefore, these factors need to be fully considered when designing and using SCs to ensure the environmental friendliness and safety of cobalt-based MOFs. These results provide an important reference for selecting and optimizing electrode materials for SCs in new energy vehicles. Furthermore, this study offers research suggestions for improving new energy materials, filling the research gaps in related fields, and supporting the further development of SC technology.

Система для экспериментальной оценки паразитных параметров интегральных мультиплексоров для электроимпедансной томографии

Physical parameters of analog multiplexer have influence on measuring, provided for electrical impedance tomography. For bio-medical application the most important is channel stray capacitance and difference among channels. Typical value is around several tens of picofarads. Integrated circuit manufactures usually do not specify this parameter and provide only typical value. Actual stray capacitance can be different from batch to batch up to several tens percentage. Parameter testing and selection can provide better quality of measurement or help to decrease influence of capacitance differences between channels. Leakage currents can cause significant influence on measurements. Especially, multiplexers lightly damaged by static electricity, can increase their leakage currents by an order of magnitude. Software and hardware system for testing of the multiplexers was developed. It can test main parameters of high voltage precision analog multiplexer, like: channels commutation, charge injection during channel switching, channels resistance, capacitance and leakage currents. Channel capacitance measurement accuracy is better than 1 pF, indeed we should substitute stray capacitance of reference multiplexer and empty test-socket. Channel capacitance measurement accuracy is around 1 Ohm, charge injection is around 1 pQ, leakage current around 100 pA. For testing we use reference multiplexer with known parameters, timer to measure charge-discharge time for capacitance estimation, precision amplifier and reed switch to measure small voltage. Replaceable sockets help test analog multiplexer not only 1 to 16 configurations, but any other configuration with smaller number of channels and even lower voltage supply if use voltage stabilizer embedded in the socket. System can check that multiplexer is fine, choose the same parameters of ICs for existing system, improve quality by choosing the ICs with the best parameters or measure them for further compensation by software.

Achieving high overall energy storage performance of KNN-based transparent ceramics by ingenious multiscale designing

(1 − x)KNN–xBCZT-based transparent ceramics with a Wrec of 7.83 J cm−3 and an η of 81.02% were obtained. High polarization boundaries and conductive mechanism transition were revealed to be the main reasons for such good performances.

Bio-Waste Argan Nut Shell-Derived Porous Activated Carbon for High Performance Supercapacitor Electrode Material

The supercapacitors (SCs) have become a great candidate for high power applications in energy storage units which bridge the gap between conventional capacitors and batteries fuels cells. This is because of their relatively higher specific energy compared to normal parallel plate capacitors, and higher power density and longer cycling stability, fast charge–discharge time, low level of heating, appropriate dimension/weight and low cost. The Carbon materials are considered as ideal electrode materials for supercapacitors, they play an important role in energy storage devices due to their large specific surface area, tunable pore size, high electrical conductivity and strong mechanical property, nevertheless most of the commercial activated carbons are produced from fossil fuel-based precursor (petroleum and coal) which made them to be expensive and environmentally non-friendly. hence the increasing focus on biomass precursors which are cheaper, readily available, renewable, structurally porous and environmentally friendly. Agriculture production and agro-industrial processes generate a large amount of waste. That can potentially be used to obtain important functional materials. Thus, it is possible to prepare activated carbon with high specific surface from various type of biomass. Taking all this into account, our work has focused on the use of Argan residues, very abundant in Morocco, for the production of activated carbons with developed porosity. The resulting material was evaluated as electrode material for the supercapacitor, Valuable strategies are the use of aqueous electrolytes and activated carbon that enable the valorization of wastes in a circular economy approach.The Argan residues (ANS, Argan Nut Shell) were ground to obtain a particle size of 1-3 mm The ACs were prepared by chemical activation with KOH in two steps: carbonization of the precursor followed by activation of the biochar. In the two-stage process, carbonization was carried out at 500 °C and in all cases, KOH is used in lentils. The following process variables were studied: activation temperature (700, 800 and 850 °C) and KOH/AS ratio (3/1 and 4/1). After the heat treatment, the samples were washed with 5 M HCl solution until neutral pH and dried (110 °C, 12 h). Activated carbons were characterized by N2 -196 °C and CO2 adsorption at 0 °C, scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS).The symmetric SC was assembled with the two identical electrodes (positive/negative) by sandwiching a filter paper as a separator (Whatman). Then, few drops of aqueous 1M H2SO4 dropped in between the electrodes. The electrochemical techniques used were Cyclic voltammetry and galvanostatic charge/discharge cycling. Cyclic voltammetry (CV) was scanned from 5 to 80 mV/s. Galvanostatic charge−discharge experiment was performed with a specific current from 0.125 to 12A.g-1. The study showed that the new mechanism used to produce the activated carbon from Argan Nut shell lead to high surface area. The optimum activated carbon obtained by operating carbonization temperature as 500°C and activation temperature at 800°C with KOH activation, with these conditions the results were (SBET =3091 m2.g-1, VT=1.52 cm3.g-1), In contrast, the symmetric two electrode system exhibits outstanding charge storage capacity, reaching a high specific capacitance ranging between 512-320 F.g−1 at 0.125 A g−1. Remarkable electrochemical performance is further demonstrated using Argan Nut Shell, with an excellent rate performance after 2500 cycles, the capacitance still remained at 92 %, indicating great cycle stability.This study demonstrated the interesting nature of Argan Nut shell to develop cost effective electrode materials for supercapacitors with high performance. To conclude, high surface area and porosity of the prepared ACs can serve as a flexible backbone for constructing wearable energy storage devices. Clearly, using biomasses are definitely the right track towards making renewable carbon materials and energy storage. Figure 1

Synergistic Effect of Nickel and Cobalt in Nanowire Array for High Energy Storage with Rapid Charge Transfer in Asymmetric Supercapacitor

AbstractWe introduce a unique asymmetric supercapacitor design that combines a vertically aligned Ni−Co alloy‐type nanowire (NiCoNW) array electrode with a graphene flakes (GFs) electrode. The sandwiching of these two electrodes enables the device to operate at a high working potential window of 2.0 V. The improved response of the device is attributed to the asymmetric design and a high charge transfer in the NiCoNWs compared with pure metals. The optimized presence of Co in the alloy increases the rate of hydroxide formation in an alkaline solution during the gas evolution reaction. The use of GFs to modify the graphite electrode (GFs@Graphite) provided a more stable response at high current densities. We obtain extremely stable cyclic voltammetry (CV) plots even at very high scan rates (500 V/s) and galvanostatic charge–discharge curves with longer charge–discharge times. The highest capacitance achieved for the assembled device (Asy‐NiCoNWs/GFs@Graphite) is 339 F/cm3 (volumetric) at a current density of 5.0 A/cm3. In addition, a remarkable cycling retention of ∼100 % is observed after 10000 continuous potential cycles.

Improving electric-energy transmission performance of LixNi1-xO linear ceramic resistors by Li+/Ni3+ ion occupation regulation for pulsed power technology

Linear ceramic resistor receives extensive attention for its great advantages of fast energy transmission in pulsed power technology. However, the research about improving the linear current-voltage characteristics and pulsed charge-discharge speed of LixNi1-xO solid solution is rarely reported. Herein, we fabricated the LixNi1-xO linear ceramic resistors through a solid-phase reaction method, and the effects of the Li+ ion on the microstructure, current-voltage characteristics and pulsed charge-discharge properties were studied. Specifically, the electron holes exchange between divalent and trivalent nickel ions is enhanced by Li substitution, which contributed to the significantly decreasing in nonlinear coefficient (α) and resistivity. On a separate note, the rising edge of pulse charge-discharge is influenced by the linearity of LixNi1-xO ceramic resistors. The closer the nonlinear coefficient is to 1, the shorter the pulsed charge-discharge time is. Meanwhile, the defect dipoles induced by Li substitution may also contribute to the reduction of discharge time of LixNi1-xO linear ceramic resistors. As a result, the Li0.03Ni0.97O linear ceramic resistor with an excellent nonlinear coefficient of 1.03 exhibits extraordinary fast discharge speed (t0.9 = 94.8 ns) at 1.0 kV. The investigation on LixNi1-xO linear ceramic resistors suggests the potential of this material to be applied in the pulsed power system.

Enhanced electrochemical performance of CNx/Co3O4 multilayer electrodes prepared by a hybrid non-thermal plasma/sol-gel method for energy storage applications

In this work, we report a direct study of the enhanced electrochemical performance of CNx/Co3O4 nano-composite multilayer electrodes which demonstrate great promise as valuable electrode materials for energy storage applications. CNx/Co3O4 electrodes were prepared by a novel hybrid non-thermal plasma/sol-gel deposition technique combining dielectric barrier discharge plasma with a C2H4/N2 gas mixture and sol-gel spin-coating methods. The results indicated that the rough and porous CNx (a-C:H:N) layer consisting of various N species (especially graphitic, pyrrolic and pyridinic N) generated by nitrogen plasma improves electrical conductivity and facilitates ion diffusion in the a-C:H:N/Co3O4 electrode. Furthermore, the synergistic effects arising from interleaving redox active Co3O4 interlayers between CNx layers involving numerous nano-pores led to the remarkable electrochemical activity of the composite electrodes. It was found that the CNx layers noticeably overcame the poor cyclic stability of Co3O4 by protecting it from dissolution in the electrolyte and these composite electrodes remained significantly stable after a very long charge-discharge time. The areal capacitance of 203.4 mF/cm2 at 3 mA/cm2 of the a-C:H:N/Co3O4 multilayer electrode enhanced by 9.7 % of the initial capacitance after 450 CD cycles and stayed stable afterward. This unique hybrid architecture showed intriguing electrochemical properties including rapid redox reactions, wide potential window of 2.73 V, high surface activity and favorable cyclic stability as well as proper reversibility of a-C:H:N/Co3O4 multilayer electrode which makes it a valuable low-cost candidate for electrochemical applications such as energy storage electrodes and biosensors.

Wavelet Packet-Fuzzy Optimization Control Strategy of Hybrid Energy Storage Considering Charge–Discharge Time Sequence

A hybrid energy storage system (HESS) can effectively suppress the high and low-frequency power fluctuations generated by wind farms under the intermittency and randomness of wind. However, for the existing power distribution strategies of HESS, power-type and energy-type energy storage have the problem of inconsistent charge–discharge states in the same time sequence, which makes it difficult to achieve optimal operation in terms of charge–discharge coordination and energy flow. To solve this problem, this study firstly adopts adaptive wavelet packet decomposition (WPD) to decompose the original wind power to acquire grid-connected power and HESS initial distribution power, to ensure that the supercapacitor and battery undertake the corresponding high and low-frequency power fluctuations, respectively; Then, for the inconsistent charge–discharge states, a charge–discharge time sequence optimization strategy based on the consistency index is proposed to correct the initial power distribution of HESS for the first time; Finally, aiming at the stage of charge (SOC) over-limit problem, the fuzzy optimization method is adopted to correct the HESS output power for the second time, which can reduce the unnecessary charge–discharge energy effectively. With typical daily output data of a 100 MW wind farm, the proposed control strategy is verified. The results show that it can make different energy storage technologies synchronously suppress wind power fluctuation in the same time sequence; compared with not considering charge–discharge time sequence optimization, the charge–discharge conversion times of the battery obtained by the proposed method are reduced from 71 to 14 times, and the charge–discharge conversion times of supercapacitor are reduced from 390 to 61 times; The cumulative reduction of unnecessary charge–discharge energy by HESS is 12.12 MWh. Besides, the SOC curves of HESS are controlled at a normal level, thus improving the economy and service life of HESS.

Achieving ultrahigh energy storage density in super relaxor BCZT-based lead-free capacitors through multiphase coexistence

Dielectric capacitors own great potential in next-generation energy storage devices for their fast charge-discharge time, while low energy storage capacity limits their commercialization. Enormous lead-free ferroelectric ceramic capacitor systems have been reported in recent decades, and energy storage density has increased rapidly. By comparing with some ceramic systems with fashioned materials or techniques, which lacks repeatability, as reported latterly, we proposed a unique but straightforward way to boost the energy storage capacity in a modified conventional ferroelectric system. Through stoichiometric ratio regulation, the coexistence of the C-phase and T-phase was obtained in 0.85(Ba1-xCax)(ZryTi1-y)O3-0.15BiSmO3-2 wt. % MnO ceramics with x = 0.1 and y = 0.15 under the proof of the combination of Rietveld XRD refinement and transmission electron microscope measurement. The Wrec of 3.90 J/cm3, an excellent value for BCZT-based ceramic at the present stage, was obtained because of the co-contribution of the optimization of electric field distribution and the additional interfacial polarization triggered at the higher electric fields. The finite element simulation and physical deduction, which fits very well with our experimental result, were also performed. As to the practical application, stable performance in a long-time cycle and frequency stability was obtained, and excellent discharge behaviors were also achieved.

Electrohydrodynamically printed solid-state Photo-electro protein micro-capacitors

The rapid development of portable and scalable electronics requires the production of high-performing, miniaturized energy storage devices with great flexibility and dimensional liberty. In recent years, printed capacitors have emerged as a promising means of meeting these demands. Printed flexible solid-state capacitors are being considered as next-generation energy storage systems because of their flexibility, portability, low cost, scalability, long cycle stability and the option of charging or discharging securely. Here we use sustainable and toxin-free photosynthetic protein complexes to fabricate solid-state flexible Photo-electro micro-capacitors as flexible power packs that are operable under indoor illumination. Electrohydrodynamic (EHD) printing was used to print biohybrid Photo-electro protein micro-capacitors that exhibited high performance uniformity and operational stability. Devices could be connected in either series or parallel configurations to modulate the operating voltage window and charge-discharge time. A specific capacitance of 110 mF g−1 was obtained at a scan rate of 10 mV s−1 and was retained at 91% of the initial value after 10,000 charge/discharge cycles at a current density of 0.063 mA g−1. Devices also displayed mechanical stability and robustness, retaining 93% of initial capacitance after 1000 cycles of bending. The data demonstrate that these micro-capacitors can deliver an economical and practical option as flexible energy storage and delivery devices for applications where exposure is primarily to indoor light.

Effects of plasma on electrochemical performance of carbon cloth-based supercapacitor

In this work, the surface of carbon cloth is treated by plasma jet to improve its hydrophilicity. The symmetrical carbon cloth-based supercapacitor is assembled with the carbon cloth treated by plasma as the active electrodes and sodium chloride solution as the electrolyte. With the discharge time (1 min, 2 min, 3 min) and working gas types (argon, air, helium) of plasma as variables, the effects of different plasma on the hydrophilicity of carbon cloth are observed, and the changes of the electrochemical properties of the supercapacitors with single or double carbon cloth electrodes treated by different plasma are studied. The contact angle test results show that the plasma of different working gases can weaken the hydrophobicity of carbon cloth, and the helium plasma can make the carbon cloth change from hydrophobicity to hydrophilicity. The electric capacity calculated by cyclic voltammetry shows that plasma can increase the electric capacity of carbon cloth-based supercapacitors. The electric capacity of carbon cloth-based supercapacitors with two carbon cloth electrodes treated by plasma is larger than that of single carbon cloth electrode treated by plasma. The argon and helium plasma with longer discharge time can significantly improve the electric capacity of carbon cloth-based supercapacitors. The galvanostatic charge-discharge curve shows that different working gases of plasma can make carbon cloth-based supercapacitors obtain pseudocapacitance, increase the charge-discharge time and electric capacity. From the AC impedance spectrum, it can be concluded that the plasma of any kind of working gas can reduce the impedance and charge transfer resistance of the carbon cloth-based supercapacitor. The longer plasma discharge time lead to the smaller impedance, and the impedance of the supercapacitor with both carbon cloth electrodes treated by plasma is smaller.

Planar on-chip micro-supercapacitors based on reduced graphene oxide and carbon nanotube by liquid–air interface self-assembly and photolithography

Recently, the development of miniaturized electronic devices has accelerated the demand for the rate capability of planar on-chip micro-supercapacitors (POMSs). The POMSs based on reduced graphene oxide and carbon nanotube (rGO/CNT) composite electrodes (rGO/CNT-POMSs) were manufactured in the work and detailed electrochemical tests of devices were carried out over a wide range of scanning rates (0.01–10000 V s−1). The rGO/CNT composite electrode films without binder were prepared on silicon substrates by a modified liquid–air interface self-assembly method and a hydroiodic acid reduction method. The electrodes were fabricated into interdigital structure with 50 μm width of electrode and gap of electrode by photolithography. Interdigital POMSs based on different electrodes were prepared by gold sputtering on the electrode lugs. The area capacitance of the rGO/CNT-POMSs was 28.62 μF cm−2. They also had 0.004 μWh cm−2 of energy density and 1.068 μW cm−2 of power density. In addition, the charge–discharge time constant of the device was only 5.6 μs, and the charge–discharge rate was very quick. After 10,000 cycles of charge–discharge, the capacitance retention rate was still above 88%. At the ultra-high scan rate of 10000 V s−1, the devices still worked well. Compared with the POMSs based on reduced graphene oxide electrodes (rGO-POMSs) and the POMSs based on carbon nanotube electrodes (CNT-POMSs), the introduction of the CNT significantly increased the area capacitance, energy density and power density of rGO/CNT-POMSs, and significantly shortened the charge–discharge time constant. This indicated that the rGO/CNT composite electrodes had a good application prospect in the micro-chip accumulator devices.

An SVPWM Algorithm for a Novel Multilevel Rectifier with DC-Side Capacitor Voltage Balance

The recently proposed novel unidirectional multilevel rectifier, a three single-phase star-connected multilevel rectifier, has the characteristic of having a large number of DC-side capacitors and a complex capacitor voltage balancing control structure under conventional carrier-based phase-shift sine wave pulse-width modulation (SPWM). Hence, a space vector pulse-width modulation (SVPWM) algorithm for the novel multilevel rectifier is proposed in this paper, which can quickly balance the capacitor voltage without an additional voltage balancing control structure. Firstly, it divides the space vectors of the rectifier, then it determines the two basis voltage vectors that synthesize the output reference voltage. After that, based on the analysis of the relationship between switching states and the charge–discharge of capacitors, the final action sequences of redundant vectors are determined according to the principle of keeping the capacitor charge–discharge time consistent. Thus, the capacitor voltages can be automatically balanced without an additional voltage balancing control structure. Finally, simulation and experimental results validated the feasibility and effectiveness of the proposed SVPWM algorithm. The results also show improvements in current quality, capacitor voltage balance and the fluctuation of the neutral point voltage on the DC-link, allowing for further reduction in the overall volume and cost of the rectifier.

Gel polymer electrolyte with alkaline aquatic colloidal graphene for flexible and rechargeable zinc air batteries

The alkaline gel polymer electrolyte, polyvinyl alcohol (PVA)-sodium polyacrylate (PANa)-aquatic colloidal graphene (ACG)-KI (PVA-PANa-ACG-KI), was prepared by solution casting method. Fourier transform infrared spectrometer (FTIR), scanning electron microscope (SEM), electrochemical impedance spectra (EIS), cyclic voltammetry (CV) and water retention were used to study the performance of PVA-PANa-ACG-KI gel polymer electrolyte. The results show that the ionic conductivity of PVA-PANa-ACG-KI is 283.7 mS·cm–1, the electrochemical stability window is 2.6 V, and the water retention is 73.4%. The discharge capacity of the flexible zinc air batteries (ZABs) with PVA-PANa-ACG-KI gel polymer electrolyte is 803.56 mAh gZn–1, the continuous charge-discharge time is 62 h, the cycle efficiency is 74.2%, and the self-discharge rate is 0.36%. After the charge-discharge cycle, the GPE is recycled and put into use again, which effectively reduces the cost. Finally, the advantages and prospects of flexible ZABs are demonstrated, and the feasibility of flexible ZABs is proved.

Porous 3D columnar-sphere of NiO nanomaterials synthesized for supercapacitors via hydrothermal route: impact of thiourea concentration.

The charge storage application has witnessed a dramatic increase in terms of the short charge-discharge time of supercapacitors, specifically in highly active electrode materials. For charge storage supercapacitor applications, highly porous materials are preferable. In this research article, thiourea acts as a leaving agent in the preparation of the porous 3D spherical architecture of NiO nanomaterials. The influence of the molar concentration of thiourea on structural, morphological, and electrochemical charge storage applications has been studied. X-ray diffraction reveals a cubic structure with Fm3̄m space group for the NiO nanomaterials. The scanning electron microscopy (SEM) images show the porous 3D columnar spherical structure, and FTIR has been used for the optical analysis of the NiO materials. The 1D-3D columnar-spherical structure of the NiO flakes exhibits a high electrochemical charge storage pseudocapacitive nature. The optimized 0.40 M thiourea-NiO (Th-NiO) nanomaterial is highly hydrophilic, exhibiting a maximum specific capacity of 171.1 mA h g-1 at 5 mV s-1 by CV and 148.5 mA h g-1 at 0.2 mA cm-2 by GCD. The highest power, energy densities are 0.96 kW kg-1 and 6.66 W h kg-1 with the highest charge-discharge cycle rating of 92% up to 5000 cycles of the asymmetric NiO//rGO hybrid supercapacitor device.

Significantly Enhanced Energy Storage Performance of Lead-Free BiFeO3-Based Ceramics via Synergic Optimization Strategy.

Owing to the merits of giant power density and ultrafast charge-discharge time, dielectric capacitors including ceramics and films have inspired increasing interest lately. Nevertheless, the energy storage density of dielectric ceramics should be further optimized to cater to the boosting demand for the compact and portable electronic devices. Herein, an ultrahigh recoverable energy storage density Wrec of 13.44 J/cm3 and a high efficiency η of 90.14% are simultaneously realized in BiFeO3-BaTiO3-NaTaO3 relaxor ferroelectric ceramics with high polarization Pmax, reduced remanent polarization Pr, and optimized electric breakdown strength Eb. High Pmax originates from the genes of BiFeO3-based ceramics, and reduced Pr is induced by enhanced relaxor behavior. Particularly, a large Eb is achieved by the synergic contributions from complicated internal and external factors, such as decreased grain size and improved resistivity and electrical homogeneity. Furthermore, the ceramics also exhibit satisfactory frequency, cycling and thermal reliability, and decent charge-discharge property. This work not only indicates that the BiFeO3-based relaxor ferroelectric materials are promising choices for the next-generation electrostatic capacitors but also paves a potential approach to exploit novel high-performance dielectric ceramics.