Total Capacitance Research Articles

CNN-Cap: Effective Convolutional Neural Network-based Capacitance Models for Interconnect Capacitance Extraction

Accurate capacitance extraction is becoming more important for designing integrated circuits under advanced process technology. The pattern matching-based full-chip extraction methodology delivers fast computational speed but suffers from large error and tedious efforts on building capacitance models of the increasing structure patterns. In this work, we propose an effective method for building convolutional neural network (CNN)-based capacitance models (called CNN-Cap) for two-dimensional (2-D) and three -dimensional (3-D) interconnect structures. With a novel grid-based data representation, the proposed method is able to model 2-D pattern structure and 3-D window structure with a variable number of conductors to largely reduce the number of patterns or increase the accuracy. Based on the ability of ResNet architecture on capturing spatial information and the proposed training skills, the obtained CNN-Cap exhibits much better performance over the multilayer perception neural network-based capacitance model while being more versatile. Extensive experiments on a 55 nm and a 15 nm process technologies have demonstrated that the error of total capacitance produced with 2-D CNN-Cap is always within 1.3%, and the error of produced coupling capacitance is less than 10% in over 99.5% probability. For 3-D structures, CNN-Cap predicts the total capacitance with less than 5% error in 99% probability and with a maximum error of 7.7%. For the tested 2-D and 3-D structures, the CNN-Cap run on a GPU server is more than 4,000× and 12,000×, respectively, faster than the conventional field solver Raphael, while consuming negligible memory.

Facile synthesis of 2D acid-etched g-C3N4 nanosheets with 1D ZnO nanorods as a promising electrode material for supercapacitor

A low-cost, non-toxic nanocomposite of two-dimensional (2D) nanosheets of acid-etched graphitic carbon nitride (TGCN) and one-dimensional (1D) nanorods of zinc oxide (ZnO NRs) is prepared using one-step calcination method. The average size and diameter of ZnO nanorods in TGCN/ZnO (T-ZnO) nanocomposite is reduced to 0.5 and 0.73 times than pristine ZnO NRs, respectively. After the acid-etching process, the size of the T-ZnO nanocomposite is further reduced which enhanced its specific surface area to 16.82 m2/g as compared to pristine ZnO NRs (3.56 m2/g). T-ZnO NRs shows a specific capacitance of 398.47 F/g using 0.5 M H2SO4 which is higher as compared to T-ZnO NRs using 0.5 M Na2SO4 (278.16 F/g) and 6 M KOH (106.10 F/g). Using Electrochemical impedance spectroscopy, diffusion coefficient (D) value 1.85 × 10−11 is obtained for T-ZnO NRs (0.5 M H2SO4). T-ZnO NRs also exhibits a higher specific capacitance of 311.80 F/g at 1 A/g using 0.5 M H2SO4. The nanocomposite shows superior energy density of 97.43 Wh/kg at 750 W/kg of power density. The superior capacitance retention (>95 %) and stable coulombic efficiency (>80 %) of T-ZnO NRs enables the nanocomposite for practical applications in energy storage devices. The electric double layer (EDL) and pseudocapacitive (PC) contribution of 6.04 % and 93.96 % to the total specific capacitance of T-ZnO NRs is evaluated using Trasatti method. The capacitive and diffusion-controlled contribution is also investigated for T-ZnO NRs using Dunn's method. The practical aspect of a supercapacitor using leakage current and self-discharge is also tested for the T-ZnO NRs. T-ZnO NRs is a promising energy storage material to fill the gap in the ongoing energy crisis.

Water in the Electrical Double Layer of Ionic Liquids on Graphene

The performance of electrochemical devices using ionic liquids (ILs) as electrolytes can be impaired by water uptake. This work investigates the influence of water on the behavior of hydrophilic and hydrophobic ILs─with ethylsulfate and tris(perfluoroalkyl)trifluorophosphate or bis(trifluoromethyl sulfonyl)imide (TFSI) anions, respectively─on electrified graphene, a promising electrode material. The results show that water uptake slightly reduces the IL electrochemical stability and significantly influences graphene's potential of zero charge, which is justified by the extent of anion depletion from the surface. Experiments confirm the dominant contribution of graphene's quantum capacitance (CQ) to the total interfacial capacitance (Cint) near the PZC, as expected from theory. Combining theory and experiments reveals that the hydrophilic IL efficiently screens surface charge and exhibits the largest double layer capacitance (CIL ∼ 80 μF cm-2), so that CQ governs the charge stored. The hydrophobic ILs are less efficient in charge screening and thus exhibit a smaller capacitance (CIL ∼ 6-9 μF cm-2), which governs Cint already at small potentials. An increase in the total interfacial capacitance is observed at positive voltages for humid TFSI-ILs relative to dry ones, consistent with the presence of a satellite peak. Short-range surface forces reveal the change of the interfacial layering with potential and water uptake owing to reorientation of counterions, counterion binding, co-ion repulsion, and water enrichment. These results are consistent with the charge being mainly stored in a ∼2 nm-thick double layer, which implies that ILs behave as highly concentrated electrolytes. This knowledge will advance the design of IL-graphene-based electrochemical devices.

Theory and Simulations of Ionic Liquids in Nanoconfinement.

Room-temperature ionic liquids (RTILs) have exciting properties such as nonvolatility, large electrochemical windows, and remarkable variety, drawing much interest in energy storage, gating, electrocatalysis, tunable lubrication, and other applications. Confined RTILs appear in various situations, for instance, in pores of nanostructured electrodes of supercapacitors and batteries, as such electrodes increase the contact area with RTILs and enhance the total capacitance and stored energy, between crossed cylinders in surface force balance experiments, between a tip and a sample in atomic force microscopy, and between sliding surfaces in tribology experiments, where RTILs act as lubricants. The properties and functioning of RTILs in confinement, especially nanoconfinement, result in fascinating structural and dynamic phenomena, including layering, overscreening and crowding, nanoscale capillary freezing, quantized and electrotunable friction, and superionic state. This review offers a comprehensive analysis of the fundamental physical phenomena controlling the properties of such systems and the current state-of-the-art theoretical and simulation approaches developed for their description. We discuss these approaches sequentially by increasing atomistic complexity, paying particular attention to new physical phenomena emerging in nanoscale confinement. This review covers theoretical models, most of which are based on mapping the problems on pertinent statistical mechanics models with exact analytical solutions, allowing systematic analysis and new physical insights to develop more easily. We also describe a classical density functional theory, which offers a reliable and computationally inexpensive tool to account for some microscopic details and correlations that simplified models often fail to consider. Molecular simulations play a vital role in studying confined ionic liquids, enabling deep microscopic insights otherwise unavailable to researchers. We describe the basics of various simulation approaches and discuss their challenges and applicability to specific problems, focusing on RTIL structure in cylindrical and slit confinement and how it relates to friction and capacitive and dynamic properties of confined ions.

Mescoporous Nickel Titanate–Titanium Oxide Complex Material for Enhanced Energy Storage Application

Materials need to be engineered to make them device-ready. A mescoporous, a combination of meso- and microporous, nickel titanate–titanium oxide (m-NTTO) complex has been synthesized here using a simple sol–gel method for making a solid-state binder-free supercapacitor from the as-prepared powder. The m-NTTO sample, well characterized using electron microscopy, N2 adsorption–desorption isotherm, X-ray diffraction, and Raman spectroscopy was tested for its energy storage capabilities. The supercapacitive performance of m-NTTO is investigated through cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and galvanostatic charge–discharge (GCD). It shows a dominant electric double-layer capacitance with a total specific capacitance of 195 F/g at 10 mV/s and fast charging and slow discharging. Additionally, it exhibits high specific capacitance, excellent cyclic stability, and high retention. Using this sample, a prototype solid-state symmetric supercapacitor device has been fabricated to demonstrate excellent electrochemical performance with high specific capacitance, energy density, and power density was obtained, which suggests that the m-NTTO is suitable candidate material for energy storage application.

Effect of Voltage Boundary Conditions on the Sensitivity and Design of Coplanar Capacitive Sensors

Coplanar capacitive sensors are widely employed in various applications due to their advantages in noninvasive evaluation, fabrication simplicity, and versatility. While there have been several experimental demonstrations, optimization of the boundary conditions and geometry is lacking. In this letter, we investigate the effect of both the voltage boundary conditions and the electrode geometry on the sensitivity with respect to an overlaid insulating layered structure. We perform electrostatic analysis using finite element simulations to study the distribution of electric fields between two coplanar electrodes, with various combinations of applied voltages and shielding electrodes beneath the sensing electrodes. By combining this analysis with variations in electrode geometry and permittivity distribution of layers, we demonstrate how specific geometries and material properties can amplify the effect of voltage boundary conditions. Our results indicate that incorporating conductive shielding electrodes can enhance the total capacitance while enabling increased sensitivity within regions close to the electrodes. Furthermore, our study reveals that conductive shielding electrodes are more effective in achieving higher sensitivity when the gap is of similar size to the electrode width. The outcomes of this research can facilitate the more efficient design of coplanar capacitive sensors, particularly for pressure sensing and proximity sensing applications where the overlaid material under test may undergo deformation.

Nanoarchitectonics of heteroatom-doped hierarchical porous carbon derived from carboxymethyl cellulose carbon aerogel and metal-organic framework for capacitive deionization

Capacitive deionization (CDI) using porous materials offers a sustainable solution for providing affordable freshwater, but the low salt adsorption rate of benchmark carbon materials significantly limit the practical implementation. Herein, we utilized carboxymethyl cellulose sodium (CMC) as the carbon skeleton to produce a composite carbon aerogel loaded with ZIF-8 (ZIF-8/CMC-CA). The presence of ZIF-8 nanoparticles improved the pore structure of the material and provides a certain pseudo capacitance by introducing N. Compared with ZIF-8 derived carbons (ZIF-8-C), the CMC provided a good three-dimensional structure for the dispersion of ZIF-8 nanoparticles, reduced the agglomeration of particles. Furthermore, numerous carboxyl and hydroxyl groups on CMC enhanced the hydrophilicity of materials. Due to the interconnected structure, ZIF-8/CMC-CA exhibited excellent conductivity, a high specific surface area, and offered suitable channels for the rapid entry and exit of ions. In a three-electrode system, the total specific capacitance of the ZIF-8/CMC-CA electrode was 357.14 F g−1. The adsorption rate of ZIF-8/CMC-CA was 2.02 mg g−1 min−1 in a 500 mg L−1 NaCl solution. This study may provide new insight for modifying and fabricating electrode materials for practical CDI applications.

Experimental study of a carbon-based planar supercapacitor in an aqueous electrolyte

One of the remarkable characteristics of supercapacitors is their ability to rapidly charge/discharge compared to a battery. The increase in the charging rate adversely affects the capacitance reduction. To address this issue, a planar interdigitated electrode that provides a good rate capability is implemented. In this paper, leveraging cyclic voltammetry, we investigate the specific capacitance of three difference patterns of carbon-based planar electrodes and conventional sandwich supercapacitors using two electrodes system of cyclic voltammetry technique. The capacitance of all planar samples reach the maximum peak, which is higher than its initial value even after increasing the scan rate by 50-fold. The narrow planar electrode fringe has a strong electric field and enhances the capacitance. The optimum applied scan rate can be manipulated by varying the electrolyte concentration. Thus, a simplified model of charge storage behavior is proposed. Furthermore, the influence of electrolyte concentration and applied scan rate on the total capacitance is discussed. The excellent rate capability observed herein demonstrates the superior electrochemical performance of supercapacitor with planar electrode configuration beyond the conventional sandwich structure.

A 99.93% energy-efficient switching scheme for SAR ADC without switching energy in the first three MSBs

This paper presents a highly energy-efficient and area-saving switching scheme for successive approximation register (SAR) analog-to-digital converters. By switching the voltages of all the bottom plates of capacitors in one side simultaneously by the same voltage level, the proposed switching scheme consumes no switching energy in the first three comparison cycles during which most of the switching energy is consumed. This switching method achieves a 99.93% reduction in switching energy and 97.6% less number of total capacitors over the conventional SAR switching scheme. In addition, the root mean square (RMS) of the maximum differential nonlinearity (DNL) and the maximum integral nonlinearity (INL) are 0.318 LSB and 0.32 LSB, respectively.

A Boost-Inductorless Electrolytic-Capacitorless Single-Stage Bidirectional Isolated AC–DC Converter

With the development of wide-bandgap devices, bidirectional isolated ac–dc converter becomes an attractive solution to realize highly compact, highly efficient power conversion for electric vehicle (EV) chargers and energy storage applications. However, in the existing literature, regardless of two-stage or single-stage isolated ac–dc converters, the circulating current in boost inductors is inversely proportional to the inductance value, resulting in large volume and high loss of the converter. In this article, a boost-inductorless electrolytic-capacitorless single-stage bidirectional ac–dc converter with high-frequency isolation is proposed. With the introduction of a center-tapped transformer, the proposed converter can achieve nearly zero circulating current without any boost inductor, thus overcoming the drawbacks mentioned above. Equivalent circuit analysis is applied to illustrate the operation principle and advantages of the proposed topology. A detailed comparison between the proposed topology and the state-of-the-art is also provided. The experimental results obtained from a 3.6 kW, 140 kHz single-phase EV charger prototype are given as the proof-of-the-concept. It is demonstrated that the proposed converter prototype realizes a peak efficiency of 96.4% with only 38 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">μ</i> H total inductance and 6.33 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">μ</i> F total capacitance.

Structural supercapacitor electrodes for energy storage by electroless deposition of MnO2 on carbon nanotube mats

Structural supercapacitors have great potential for the future of electric-powered vehicles and mobile robots, as they can serve a dual purpose of providing structural integrity and storing electric energy. However, a significant challenge in the development of these energy storage structures is the creation of electrodes that are mechanically strong and stiff. Herein, we report an electroless technique for depositing pseudocapacitive manganese dioxide (MnO2) uniformly throughout carbon nanotube (CNT) mats, resulting in multifunctional supercapacitor electrodes with simultaneously enhanced mechanical and electrochemical properties. The deposited MnO2 nanoporous material acts as a structural matrix supporting the CNTs, thus improving the strength and stiffness. Furthermore, the uniform distribution of MnO2 nanoparticles throughout the substrate reduces the through-thickness electrical resistance and achieves outstanding rate capability. With the optimum loading of MnO2 95 wt%, which gives the highest strength, the total capacitance of the electrode material increased by nine times compared to the baseline material, while the tensile strength and stiffness were improved by 110% and 430%, respectively. Employing these high-performance electrodes in supercapacitors results in improved device-level performance. Specifically, the optimum loading of MnO2 increased the device's energy density by around 100 times without compromising the power density. These new high-performance structural electrodes represent a promising technology that could accelerate the practical application of energy storage composite structures.

Reconfigurable Single-Layer Graphene Radio Frequency Antenna Device Capable of Changing Resonant Frequency.

A reconfigurable passive device that can manipulate its resonant frequency by controlling its quantum capacitance value without requiring complicated equipment has been experimentally investigated by modifying the Fermi level of large-area graphene using an external electric field. When the total capacitance change, caused by the gate bias in the passive graphene device, was increased to 60% compared to the initial state, a 6% shift in the resonant frequency could be achieved. While the signal characteristics of the graphene antenna are somewhat inferior compared to the conventional metal antenna, simplifying the device structure allowed reconfigurable characteristics to be implemented by using only the gate bias change.

Extraction of Interconnect Parasitic Capacitance Matrix Based on Deep Neural Network

Interconnect parasitic capacitance extraction is crucial in analyzing VLSI circuits’ delay and crosstalk. This paper uses the deep neural network (DNN) to predict the parasitic capacitance matrix of a two-dimensional pattern. To save the DNN training time, the neural network’s output includes only coupling capacitances in the matrix, and total capacitances are obtained by summing corresponding predicted coupling capacitances. In this way, we can obtain coupling and total capacitances simultaneously using a single neural network. Moreover, we introduce a mirror flip method to augment the datasets computed by the finite element method (FEM), which doubles the dataset size and reduces data preparation efforts. Then, we compare the prediction accuracy of DNN with another neural network ResNet. The result shows that DNN performs better in this case. Moreover, to verify our method’s efficiency, the total capacitances calculated from the trained DNN are compared with the network (named DNN-2) that takes the total capacitance as an extra output. The results show that the prediction accuracy of the two methods is very close, indicating that our method is reliable and can save the training workload for the total capacitance. Finally, a solving efficiency comparison shows that the average computation time of the trained DNN for one case is not more than 2% of that of FEM.

Examining the Design of Different Types of DM EMI Filters and Their Effect on EMI Noise and Control Characteristics for Cuk DC-DC Converter

In this paper, DM EMI filters including LC, LC with damping, and Pi and LCL filters are designed for DC-DC Cuk converter operated in BCM. Although, DM EMI is so important for any power converter, the effect of DM filter is not investigated in detail in literature with respect to control characteristics and DM noise reduction. The main contribution of this paper is comparisons of DM EMI filter topologies regarding control characteristics and EMI noise reduction which is not presented in the literature. Another contribution is to give a practical design methodology for EMI filter design avoiding complex mathematical procedures. Besides, the paper designs an LCL filter, popular for inverter applications, for Cuk converter that is not introduced in the literature. Examining the filter effect on the converter from the control point of view is a very complicated issue because a linearized model of the converter which is naturally nonlinear should be obtained. To do so, the converter’s small signal analysis must be derived. Therefore, for examining the effect of filters, a small signal analysis of the Cuk converter is made through an average state-space model. After that, transfer functions of each filter topology are obtained. Lastly, the entire transfer functions of the system using both the Cuk converter and each filter are acquired, separately. By using the transfer functions of overall systems, the effect of each filter topology is investigated by root locus and bode plots. Moreover, experimental verification of all filters is realized over a 15 W Cuk converter with a 25 kHz switching frequency. It is validated by applications that the LCL filter provides better control characteristics on the Cuk converter, the total inductor value is reduced by 30% and the total capacitor value is reduced by 25% compared to other filters. However, with respect to DM noise Pi and LC filters give better results.

A state-of-the-art review of N self-doped biochar development in supercapacitor applications

Due to its renewability, eco-friendliness, and cost-effectiveness, biochar is a promising alternative to fossil fuel-based carbon for electrode material application in supercapacitors. However, pristine biochar often exhibits poor structure and low activity, which strongly inhibit its commercial utilization. N-doping is an efficient way to improve the electrochemical performance of biochar by enhancing the conductivity and surface wettability that further induce a pseudo-capacitance effect. Compared with external doping, the synthesis of N self-doped biochar from natural N-rich biomass without using external N precursors, which are harmful and costly, has attracted increasing attention. Few reviews of N-doped biochar applications in supercapacitors are available, and studies of N self-doped biochar are still scarce. This paper reviews the developments over the past 10 years on the preparation, activation, and application of N self-doped biochar in supercapacitors. Notably, the evolution of N-functionalities during N self-doped biochar production with or without activating agents was analyzed. The relationships between N content and the specific capacitance and the contribution of N self-doping-induced pseudo-capacitance to the total specific capacitance are also discussed. Finally, the challenges and the prospects of N self-doped biochar applications in supercapacitors are proposed.

Efficient Dual Output Regulating Rectifier and Adiabatic Charge Pump for Biomedical Applications Employing Wireless Power Transfer

A power management unit (PMU) is an essential block for diversified multi-functional low-power Internet of Things (IoT) and biomedical electronics. This paper includes a theoretical analysis of a high current, single-stage ac-dc, reconfigurable, dual output, regulating rectifier consisting of pulse width modulation (PWM) and pulse frequency modulation (PFM). The regulating rectifier provides two independently regulated supply voltages of 1.8 V and 3.3 V from an input ac voltage. The PFM control feedback consists of feedback-driven regulation to adjust the driving frequency of the power transistors through adaptive buffers in the active rectifier. The PWM/PFM mode control provides a feedback loop to adjust the conduction duration accurately and minimize power losses. The design also includes an adiabatic charge pump (CP) to provide a higher voltage level. The adiabatic CP consists of latch-up and power-saving topologies to enhance its power efficiency. Simulation results show that the dual regulating rectifier has 94.3% voltage conversion efficiency with an ac input magnitude of 3.5 Vp. The power conversion efficiency of the regulated 3.3 V output voltage is 82.3%. The adiabatic CP has an overall voltage conversion efficiency (VCE) of 92.9% with a total on-chip capacitance of 60 pF. The circuit was designed using 180 nm CMOS technology.

Exploring the origin of pseudocapacitive energy storage differences for molybdenum nitride-based electrodes

Molybdenum nitride-based materials have been extensively investigated as pseudocapacitive materials due to their superior metallic conductivity and thermal stability. Nevertheless, few studies have focused on the origin of pseudocapacitance (Credox) differences for charged molybdenum nitride electrodes with different crystal structures. Herein, taking cubic Mo2N (NaCl-type), Mo3N2 (CsCl-type) and hexagonal MoN (AlB2-type) as the research targets, we have systematically investigated the differences in rate performance and capacitance of these three materials by experimental methods and density functional theory (DFT) calculations to obtain the origin of Credox differences among them. DFT calculations prove that the proportions of Credox are 86.45%, 85.32% and 84.57% for Mo2N, Mo3N2 and MoN and thus the Mo2N features the most obvious pseudocapacitive behavior. Furthermore, the rigid band approximation (RBA) method reveals that the differences of work function change (ΔWF) are the root cause of Credox differences for these three kinds of charged materials. The highest electrochemical capacitance retention, highest conductivity, and fastest K+ ion mobility indicate that the MoN possesses the best rate performance among these three materials. Additionally, the most intact nanowire morphology and smallest ΔWF of Mo2N enable it to possess the highest electrochemical capacitance and theoretical total capacitance (Ctotal). The above findings will shed light on examining capacitance in a charged environment while screening the next-generation high-performance pseudocapacitive materials under various crystal structures.

Scalable Charge-Based Compact Model for Drain Current in Fin-Shaped GaN HEMTs

We present a novel charge-based compact model for drain current in fin-shaped GaN high-electron-mobility transistors (Fin-HEMTs). A positive threshold voltage shift is observed in Fin-HEMTs due to better gate control of the channel. The combined effect of top and side gates on the channel charge density is studied with the help of detailed TCAD simulation. For the first time, a closed-form expression for 2-D electron gas (2-DEG) density in Fin-HEMTs is derived. The fin width dependence of the 2-DEG current is modeled in a unique way by considering the modified gate capacitance and threshold voltage in Fin-HEMTs. The total drain current is modeled as the sum of 2-DEG and double-gate field effect transistor (FET) currents. In addition, the total gate capacitance including the side-gate capacitance for fin structure is also formulated. The model is generic and can be used for different fin geometries using the proposed equivalent circuits as demonstrated. A fin-width-dependent thermal resistance model is proposed and included in the drain current model using a thermal subcircuit. The proposed model is completely analytical and does not require any iteration or fitting parameters in contrast to the available models discussed in the literature. Our model shows excellent agreement with the state-of-the-art experimental data.

Size Effect of Electrolyte Ions on the Electric Double-Layer Structure and Supercapacitive Behavior

Finding a viable electrolyte for next-generation supercapacitors is of primary importance for developing supercapacitors with high power and energy densities. Herein, we synthesized a conducting salt, tetramethylphosphonium tetrafluoroborate (TMPBF4), and compared the electrochemical characteristics of supercapacitor devices containing TMPBF4 or 1,1-dimethylpyrrolidinium tetrafluoroborate (DMPBF4). The TMPBF4 salt was selected based on the generally accepted design rule that smaller ions and solvation shells contribute to higher energy and power densities. However, at a low current density (0.1 A g–1), supercapacitors with TMPBF4 in acetonitrile (AN) exhibited a slightly lower capacitance (24.6 ± 0.1 F g–1) than those with DMPBF4 (25.0 ± 0.2 F g–1). Clarification of this behavior using electrochemical and theoretical methods revealed that the total capacitance is influenced by not only the size of the ions but also the degree of cation–anion interactions near the electrodes. By contrast, at a high current density of 10 A g–1, supercapacitors with TMPBF4 showed an 18% increase in capacitance relative to those with DMPBF4. Supercapacitors with TMPBF4 exhibited both high capacitance and a remarkably long cycle life (10,000 cycles) at a high working voltage (3.2 V) and high current density (10 A g–1). Furthermore, supercapacitors utilizing TMPBF4/AN provided a sufficiently fast frequency response for 60 Hz alternating current (ac) line filtering. These insights into the influence of the investigated electrolyte salts on the formation of electric double-layer structures offer design rules for developing electrolytes for supercapacitors.

Designing of a Free-Standing Flexible Symmetric Electrode Material for Capacitive Deionization and Solid-State Supercapacitors

In this work, a highly efficient free-standing flexible electrode material for capacitive deionization and supercapacitors was reported. The reported porous carbon shows a high surface area of 2070.4 m2 g–1 with a pore volume of 0.8208 cm3 g–1. The material exhibited a high specific capacitance of 357 F g–1 at 1 A g–1 in a two-electrode symmetric setup. A solid-state supercapacitor device has been fabricated with a total cell capacitance of 152.5 F g–1 at 1 A g–1 in a solid PVA/H2SO4 gel electrolyte with an energy density of 21.18 W h kg–1 at a 501.63 W kg–1power density. A long-run stability test was carried out up to 15,000 cycles at 5 A g–1 that showed capacitance retention of 99% with ∼100% Coulombic efficiency. Furthermore, the electrosorption experiment was conducted by a flow-through test by coating on commercially available cellulose thread that was employed, which shows electrosorption ability up to 16.5 mg g–1 at 1.2 V in a 500 mg L–1 NaCl solution. Complete experiments were conducted with a proper procedure, provided by scientific approaches with analytical data. Thus, the reported electrode material showed bifunctional application for energy storage and environmental remediation.