Active Material For Supercapacitors Research Articles

Solution Processing of Spinel Nickel Cobaltite: Exfoliation Mechanism, Dispersion Stability, and Applications.

The exfoliation of nonlayered materials to mono- or few-layers is of growing interest to realize their full potential for various applications. Nickel cobaltite (NiCo2O4), which has a spinel crystal structure, is one such nonlayered material with unique properties and has been utilized in a wide range of applications. Herein, NiCo2O4 is synthesized from NiCo2- Layered double hydroxides using a topochemical conversion technique. Subsequently, bulk NiCo2O4 is exfoliated into mono- or few-layer nickel cobaltene nanosheets using liquid-phase exfoliation in various low-boiling point solvents. An analytical centrifuge technique is also utilized to understand the solute-solvent interactions by determining their dispersion stability using parameters such as the instability index and sedimentation velocity. Among the studied solvents, water/isopropyl alcohol cosolvent is found to have better dispersion stability. In addition, density functional theory calculations are carried out to understand the exfoliation mechanism. It is found that the surface termination arising from the Co-O bond needs the least energy for exfoliation. Furthermore, the obtained nickel cobaltene nanosheets are utilized as an active material for supercapacitors without any conductive additives or binders. A solid-state symmetric supercapacitor delivers a specific capacitance of 10.2 mF cm-2 with robust stability, retaining ∼98% capacitance after 4000 cycles.

Conversion of N-doped biochar from carotenoid-extracted Tetraselmis suecica and its application to produce supercapacitors

Microalgae are one of the promising feedstocks for biorefinery, contributing significantly to net-zero emissions through carbon capture and utilization. However, the disposal of microalgal byproducts from the manufacturing process causes additional environmental pollution, thus, a new application strategy is required. In this study, the Tetraselmis suecica byproduct from the carotenoid extraction process was carbonized and converted into biochar. The converted biochar was proved to be nitrogen-doped biochar (NDB), up to 4.69%, with a specific surface area of 206.59 m2/g and was used as an electrode for a supercapacitor. The NDB electrode (NDB-E) in half-cell showed a maximum specific capacitance of 191 F/g. In a full-cell test, the NDB-E exhibited a high energy density of 7.396 Wh/kg and a high-power density of 18,100 W/kg, and maintained specific capacity of 95.5% after charge and discharge of 10,000 cycles. In conclusion, our study demonstrated that the carotenoid-extracted microalgal byproducts are a useful resource for the supercapacitor production. This approach is the first to convert T. suecica into active materials for supercapacitors.

Exceptionally high-rate production of few-layer MoS2 by a scalable and cost-effective gas-driven shear exfoliation method and its application for supercapacitors

Two-dimensional (2D) few-layer molybdenum disulfide (MoS2) is a versatile future electronic material with fascinating unique properties, but the commercialization of its’ applications is still hampered by high-rate production of few-layer MoS2 flakes on low-cost. Herein, we present a simple, scalable and cost-effective gas-driven shear exfoliation method for producing high-aspect-ratio few-layer MoS2 flakes with exceptionally high production rate. The gas-driven exfoliated MoS2 flakes, with an average thickness of 3 nm, show a reasonable large lateral dimension, with more than 10% of the flakes >1.0 μm and ∼73 % of the flakes in the range of 0.3–1.0 μm. In a lab-scale setup, the production rate reaches an impressive high value of 1.23 g/h, while the exfoliation energy consumption is as low as 0.175 kW⋅h/g. At an industrial level, the production rate can exceed 3 kg/h, marking a significant advancement towards the mass production of few-layer MoS2 on low-cost. As a proof-of-concept, the as-exfoliated few-layer MoS2 was employed as an active material for supercapacitor, which exhibited a good electrochemical performance with the specific capacity of 101.8 mAh/g. After 5000 cycles, the capacitance retention sustained at a high level of 92.9%.

Graphene as an Active Material for Supercapacitors: A Machine Learning Approach

<p class="Abstract">Graphene is a promising material for supercapacitors due to its unique properties, which influence the device's supercapacitor. This study aims to investigate the key factor of graphene properties in supercapacitors (, with the goal of improving their performance. Also, we observe the machine learning models for predicting capacitance of supercapacitor including four algorithms of machine learning: Linear Regression (LR), lazy IBK, Decision Table (DT), and Random Forest (RF). Machine learning model showed that the RF model demonstrated the highest correlation value of 0.745, surpassing other models. Also, the study revealed that graphene has a high specific surface area and highly porous structure, which enhanced the high capacitance values. Finally, these machine learning models are suitable to apply in materials sciences field for understanding the materials properties in supercapacitor.</p>

Self-standing multiwalled carbon nanotubes/polypyrrole foams for aqueous symmetric supercapacitors

Developing lightweight structures employing materials with large capacitance is desirable to diversify the employment of supercapacitors in portable electronics. Here, hollow and flexible MWCNT/PPy foams were fabricated by electropolymerization to take advantage of the PPy properties and use it as a current collector and active material for supercapacitors. The effect of the formation time of the foams was evaluated using spectroscopic and electrochemical techniques, finding the best performance after 1200 s. Using a three-electrode arrangement, this foam reached a specific capacitance of up to 450 F g−1 (@ 0.5 A g−1) in 1 M H2SO4. As a result, a symmetric supercapacitor with performance comparable to those currently reported for polypyrrole-based materials was assembled. Moreover, the assembled device herein delivered specific energy of 12.5 W h kg−1 at a specific power of 200 W kg−1, and 9.1 W h kg 1 at 4000 W Kg−1. The main reason for the capacitance fading during the galvanostatic cycling was the increment of the electric series resistance, derived from the structural stress experienced by the PPy in the foam, as shown by the morphological characterization after prolonged cycling.

Construction of high-capacitance carbonate-rich bimetallic layered (hydr)oxides onto ZIF-67–derived Co/CoO-N-carbon hybrid cubes for high-performance symmetric supercapacitors

Herein, we fabricated carbonate-rich bimetallic layered hydr(oxides) (CoMnOx), which are primarily used as active materials for supercapacitors, using a simple hydrothermal method. CoMnOx was deposited onto cobalt oxide (CoO), which was produced by pyrolyzing ZIF-67 at 800 °C under N2 atmosphere. The Co/CoO cubes synthesized using carbonized ZIF-67 (ZIFC) were covered with CoMnOx shells with high reduction efficiency and abundant Co active sites and surface O species. The effects of the carbonate species present between the CoMnOx layers and at the surface of the hybrid CoMnOx@ZIFC materials were evaluated using PXRD and XPS. The peaks at the binding energies of 290 and 400 eV in the C 1s and N 1s XPS profiles of CoMnOx@ZIFC, respectively, indicate the presence of carbonate species and coordination of CoO and Co with the N-rich carbon materials, respectively. The FE-SEM images of CoMnOx@ZIFC revealed the partial decomposition of the cubic structure of ZIFC, which agreed with previously reported data. Moreover, the elemental composition of CoMnOx@ZIFC was confirmed using EDS mapping and point analysis. The CoMnOx@ZIFC electrodes exhibited a remarkable specific capacitance/capacitor of 963 F g−1/588 C g−1 at 1 A g−1 and excellent cycling stability over 1000 cycles, which was superior to those of previously reported MOF-derived carbonate-based materials in alkaline electrolytes. The CoMnOx@ZIFC||CoMnOx@ZIFC symmetric supercapacitor exhibited an energy density of 60.75 W h kg−1 with a power density of 5947 W kg−1 and an exceptional cycling stability (>99.5 %) after 3000 cycles.

Dual Ni/Co-hemin metal–organic framework-PrGO for high-performance asymmetric hybrid supercapacitor

In this study, we conducted direct synthesis of a dual metal–organic framework (Ni/Co-Hemin MOF) on phosphorous-doped reduced graphene oxide (PrGO) to serve as an active material in high-performance asymmetrical supercapacitors. The nanocomposite was utilized as an active material in supercapacitors, exhibiting a noteworthy specific capacitance of 963 C g−1 at 1.0 A g−1, along with a high rate capability of 68.3% upon increasing the current density by 20 times, and superior cycling stability. Our comprehensive characterization and control experiments indicated that the improved performance can be attributed to the combined effect of the dual MOF and the presence of phosphorous, influencing the battery-type supercapacitor behavior of GO. Additionally, we fabricated an asymmetric hybrid supercapacitor (AHSC) using Ni/Co-Hemin/PrGO/Nickel foam (NF) and activated carbon (AC)/NF. This AHSC demonstrated a specific capacitance of 281 C g−1 at 1.0 A g−1, an operating voltage of 1.80 V, an impressive energy density of 70.3 Wh kg−1 at a high power density of 0.9 kW kg−1. Notably, three AHSC devices connected in series successfully powered a clock for approximately 42 min. These findings highlight the potential application of Hemin-based MOFs in advanced supercapacitor systems.

Cerium-based metal–organic framework-conducting polymer nanocomposites for supercapacitors

Nanocomposites consisting of a cerium-based metal–organic framework (Ce-MOF-808) and a conducting polymer, poly(3,4-ethylenedioxythiophene) (PEDOT), are synthesized by performing the pulse electrodeposition of PEDOT within the Ce-MOF-808 thin films. Ratios between MOF and PEDOT in the composites are tunable by simply adjusting the charge density used for electropolymerization, and the crystallinity, morphology, and elemental distributions of the resulting nanocomposites are characterized. Electrochemical behaviors and capacitive performances of the pristine MOF, pristine PEDOT thin films, and composite thin films are investigated with the use of the neutral sodium sulfate aqueous electrolytes. The reversible electrochemical reactivity of the highly porous Ce-MOF-808 provides a pseudocapacitance, and the electronically conducting PEDOT can not only offer a remarkable double-layer capacitance but also facilitate the electronic conduction between the redox-active cerium sites present in the MOF. As a result, the composite can outperform both the pristine MOF and pristine electrodeposited PEDOT as the active materials for supercapacitors. Findings here suggest that the highly porous and redox-active cerium-based MOF thin films are capable to enhance the capacitive performances of the electrodeposited PEDOT thin films.

Heteroatom (N, P)-driven carbon nanomaterials for high-energy storage in supercapacitors

Nanoflower-like hollow carbon sphere (CS) materials with two different heteroatoms doping (N, P) were prepared by a simple synthetic method (NPCS). The specific surface area of NPCS can reach a high value of 396 m2/g. The NPCS has a high degree of hollowness and the self-assembled nanosheet of NPCS forms a fast electron transport channel, and also increases active area in contact with electrolyte. The doping of heteroatoms increases the defect level of the carbon-based nanomaterials and changes the local electron state of the material, thus forming storage sites on the surface of the material, which can be used as a station for ions collecting and distributing. The material was studied as an active material for supercapacitors, and the specific capacitance reached 274.9 F/g. After the 4000th cycle stability test, it still maintained 95.2% of the specific capacitance, indicating that the material has excellent properties of supercapacitor materials.

A high performance PEDOT/PPy composite electrode enabled by regulating molecular growing orientation

The conductive polymer is a promising candidate for energy storage devices due to its flexibility, light weight, and low cost. Polypyrrole (PPy) has been widely investigated as active material in supercapacitors. Here, conductive Poly (3,4-ethyldioxythiophene) (PEDOT) is used as a substrate for electropolymerization of PPy. The counterion CF3SO3- of PEDOT can adjust the electropolymerization rate and molecular growing orientation of PPy. Therefore, the mass capacitance of the composite electrode (PEDOT/PPy) reaches a top value of 551 F/g, at 2 A/g in 1 M H2SO4 electrolyte. This value outperforms the PPy electrode on the ITO substrate by around 53.9%. Moreover, the composite electrode (PEDOT/PPy) shows better stability compared to the PPy on the ITO substrate. This study provides a new route for the preparation of high electrochemical performance conductive polymer composite electrodes.

Synthesis of vanadium metal-organic framework, characterization, and study of electrochemical properties for using in supercapacitor and oxygen evolution reaction

Transition-metal (V) based metal–organic framework drew a lot of attention for use in upcoming generation electrochemical energy storage devices (Supercapacitors) and energy production during oxygen evolution reaction (OER). The large surface area, the exposed metal sites, and structural controllability make MOFs preferred heterogeneous catalysts for various catalytic reactions. Due to their tunable structures and high porosity, MOFs have shown favorable applications as electrode materials for supercapacitors. This investigation synthesized V-MOF nanorods by hydrothermal and microwave methods. The NiCo2S4/V-MOF@rGO synthesized offered a maximum specific capacitance of 1844F/g at a current density of 1.0 Ag−1. Moreover, an asymmetric supercapacitor NiCo2S4/V-MOF@rGO//AC exhibits a high energy density of 800 Wh kg−1 at a power density of 61.10 W kg−1 and 98 % of its capacitance retention after 3000 cycles. In another part of this study, the V-MOF synthesized in the previous step showed an excellent electrocatalytic performance toward the OER. Furthermore, by compositing it with graphene sheets and doping it with phosphorus as a heteroatom, its electrocatalytic activity toward OER was further enhanced, showing160 mV overpotential at a current density of 10 mA cm−2 in a 3.0 M KOH after 1000 sweeps aqueous solution. This researches present a simple, efficient, and high-performance electrocatalyst for OER and active material for supercapacitors.

Yerba mate: From waste to activated carbon for supercapacitors

Developing technological solutions that use yerba mate waste as precursors is key to reducing the environmental impact caused by the lack of treatment and its accumulation in landfills. Due to their physicochemical properties, these residues can be used to develop activated carbons. Activated carbon is a versatile material with a high surface area that can be used for energy storage.In this work, yerba mate residues were valued by producing chemically activated carbon to be used as electrode material in supercapacitors. Activated carbons were developed through chemical activation in two steps with KOH. Variables such as impregnation ratio and activation temperature are studied. The developed carbons were characterized by physicochemical and electrochemical techniques. They were found to have high surface areas, up to 1800 m2 g-1, with a hierarchical porous distribution. A maximum specific capacitance of 644 F g-1 at 0.1 A g-1, and power values of ca 32,000 W kg-1, at 33 A g-1 were found. All the synthesized carbons have excellent electrochemical properties and are suitable for use as active material in supercapacitors.

3D Printed Thick Reduced Graphene Oxide: Manganese Oxide/Carbon Nanotube Hybrid Electrode with Highly Ordered Microstructures for Supercapacitors

AbstractHigh capacitance and good rate performance supercapacitors are needed to power sensors and miniaturized electrical devices. Thick electrodes are promising to increase the mass loading of active materials in supercapacitors, but the 3D geometries and microstructures in thick electrodes still hinder the development with high electron and ion exchange rate and accessible active sites. The scaffold 3D electrodes of reduced graphene oxide:manganese oxide/carbon nanotube (rGO:MnOx/CNT) are manufactured by material extrusion 3D printing (ME3DP), where the mass ratio of rGO to MnOx/CNT composites, thickness, and mass loading per unit area are controllable. The increasing amount of MnOx/CNT composites boosts the areal capacitance. Although the rate capability decays fast with the increasing of MnOx/CNT, it remains stable at different thicknesses (1.2, 1.6, and 2 mm). 2 mm thick rGO:MnOx/CNT (weight ratio 5:3) electrode exhibits an area capacitance of 302.13 mF cm−2 at a current density of 0.5 mA cm−2, due to the highly ordered rGO networks. Compared to the casted electrodes, the microstructures in the 3D printed electrode contribute to lower resistances for the charge and ion transportation.

Synthesis and investigation of CoMnFeO4/reduced graphene oxide as ecofriendly electrode material for supercapacitor and its electrochemical performances

In recent years, due to the superiority of clean and renewable energy and the need for suitable storage systems for this energy, supercapacitors have been studied and investigated as a suitable storage device. For the design and manufacture of supercapacitors, the structure of the used electrode and the configuration of the device are among the most effective parameters. Therefore, in this study, the aim is to design and investigate a suitable and cost-effective nanomaterial for use in supercapacitors. For this purpose, CoMnFeO4 magnetic nanoparticles and rGO/CoMnFeO4 magnetic nanocomposite were synthesized. Then, they were investigated and identified using FT-IR, XRD, VSM, SEM, Mapping and EDX analyses. In order to investigate the supercapacitance property of these materials, various electrochemical analyses such as cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and electrochemical impedance spectroscopy (EIS) were used. The specific capacity, the energy density, and the power density were calculated at different conditions. The specific capacity and the energy density of rGO/CoMnFeO4 at a current density of 1 A.g−1 are 380 F.g−1 and 58.18 Wh.kg−1, respectively. The results of this study generally show that CoMnFeO4 nanoparticles have the appropriate behavior as active materials for supercapacitors, and their modification with reduced graphene oxide (rGO) improved their electrochemical behavior.

Functionalized Graphene-MoO2 frameworks: An efficient electrocatalyst for iron-based redox flow battery and supercapacitor application with enhanced electrochemical performances

Grid level energy storage systems have gravitated towards redox flow batteries due to their great performance, economic factors and supercapacitors have gained prime importance as they bridge the void between batteries and capacitors. The electrochemical behavior of the Iron redox flow battery is directly co-related to the positive electrode. Herein the positive electrode is modified with able metal oxide and graphene-based composite to increase the electrochemical activity of the system. MoO2-GP was synthesized using one-step hydrothermal process and characterized by XRD, SEM, EDAX, TEM, XPS, and Elemental mapping. Different Electrochemical techniques are evidenced for significant anodic and cathodic peak current densities, least charge transfer resistance, least solution resistance, reversibility, and reduced polarization resistance. A 132 cm2 IRFB with composite modified positive electrode showcased improved CE, VE, and EE. Wherein the MoO2-GP composite was also incorporated as an active material for supercapacitors, focusing to increase the stability and the Cs of the system. The combined effect of electrical double layer capacitance (EDLC) and pseudocapacitive or faradaic nature of composite material, contributed to the increased electrochemical activity of supercapacitors. The results demonstrate that the MoO2-GP composite material leaps providing better active sites, improving the reactions thus acting as an excellent electrochemically active material for energy storage devices.

Effects of carbonization temperature on fabricating carbonized Universitetet i Oslo-66 as active materials for supercapacitors

Universitetet i Oslo-66 (UiO-66) with high surface area and tunable pore structure is considered as one of efficient active materials of supercapacitors (SC). Carbonization is largely used to enhance electrical conductivity and energy storage ability of active material, but the parameters for carbonizing UiO-66 as active material of SC is rarely studied. It is the first time to investigate carbonization temperature effects on physical properties of UiO-66 derived carbon and electrochemical performances of SC. Applying higher temperatures for carbonizing UiO-66 leads to more serious structure shrinking, more defects and more C–O than CO bonds in carbon materials, but the recrystallization at 900 ​°C causes larger particle formation. The carbonized UiO-66 prepared using 800 ​°C (C800) shows the highest specific capacitance of 169.7 ​F/g at 20 ​mV/s, due to small particle size and suitable ratios of C–O to CO and graphene to defect. The SC composed of C800 electrodes shows maximum energy density of 2.55 ​Wh/kg at power density of 200 ​W/kg and excellent charge/discharge cycling stability with capacitance retention of 86.5% and Coulombic efficiency of 100% after 12000 times repeatedly charge/discharge process. Excellent bending ability is also achieved for this SC with capacitance retention of 74.3% after bending 500 times at 180°.

Autonomous Chemistry Enabling Environment-Adaptive Electrochemical Energy Storage Devices

Autonomous Chemistry Enabling Environment-Adaptive Electrochemical Energy Storage Devices

Constructing a Carbon-Encapsulated Carbon Composite Material with Hierarchically Porous Architectures for Efficient Capacitive Storage in Organic Supercapacitors

Hierarchical porous activated carbon (HPAC) materials with fascinating porous features are favored for their function as active materials for supercapacitors. However, achieving high mass-loading of the HPAC electrodes remains challenging. Inspired by the concepts of carbon/carbon (C/C) composites and hydrogels, a novel hydrogel-derived HPAC (H-HPAC) encapsulated H-HPAC (H@H) composite material was successfully synthesized in this study. In comparison with the original H-HPAC, it is noticed that the specific surface area and pore parameters of the resulting H@H are observably decreased, while the proportions of nitrogen species are dramatically enhanced. The free-standing and flexible H@H electrodes with a mass-loading of 7.5 mg/cm2 are further prepared for electrochemical measurements. The experiments revealed remarkable reversible capacitance (118.6 F/g at 1 mA/cm2), rate capability (73.9 F/g at 10 mA/cm2), and cycling stability (76.6% of retention after 30,000 cycles at 5 mA) are delivered by the coin-type symmetric cells. The cycling stability is even better than that of the H-HPAC electrode. Consequently, the findings of the present study suggest that the nature of the HPAC surface is a significant factor affecting the corresponding capacitive performances.

Novel synthesis of sulfur-doped graphitic carbon nitride and NiCo2S4 composites as efficient active materials for supercapacitors

Graphitic carbon nitride (g-C3N4) with high nitrogen contents and excellent thermal/chemical stability is widely applied as active material of supercapacitors (SC). Small surface area and electrical conductivity of g-C3N4 lead to poor electrochemical performance, which can be improved by heteroatom doping and metal compound incorporation. In this work, it is the first time to fabricate NiCo2S4/S-doped g-C3N4 (NCS-C) composite using thermal polymerization and hydrothermal reaction as active material of SC. The S-g-C3N4 electrode shows a higher specific capacitance (Csp) of 72.4 mF/g at 20 mV/s than that of 49.5 mF/g of g-C3N4 electrode. Using sulfur as doping source and anion in metal compound favors for improving compatibility of composites. NCS-C composite shows favorable S-g-C3N4 nanosheets-covered NCS flower-like structures. The NCS-C electrode presents a higher Csp value of 351.0 F/g at 1 A/g (886.2 F/g at 20 mV/s) than that of 348.9 F/g at 1 A/g (794.2 F/g at 20 mV/s) of NCS electrode, due to sulfur and nitrogen-rich carbon of S-g-C3N4 and abundant redox reactions of NCS. The symmetric SC with NCS/C electrodes delivers potential window of 1.0 V, maximum energy density of 9.7 Wh/kg at 0.65 kW/kg, and Csp retention of 97.6% and Coulombic efficiency of 90% after 10,000 charge/discharge cycles.

Design of manganese dioxide for supercapacitors and zinc-ion batteries: similarities and differences

Energy storage devices, e.g., supercapacitors (SCs) and zinc-ion batteries (ZIBs), based on aqueous electrolytes, have the advantages of rapid ion diffusion, environmental benignness, high safety and low cost. Generally, SCs provide excellent power density with the capability of fast charge/discharge, while ZIBs offer high energy density by storing more charge per unit weight/volume. Although the charge storage mechanisms are considered different, manganese dioxide (MnO2) has proven to be an appropriate electrode material for both SCs and ZIBs because of its unique characteristics, including polymorphic forms, tunable structures and designable morphologies. Herein, the design of MnO2-based materials for SCs and ZIBs is comprehensively reviewed. In particular, we compare the similarities and differences in utilizing MnO2-based materials as active materials for SCs and ZIBs by highlighting their corresponding charge storage mechanisms. We then introduce a few commonly adopted strategies for tuning the physicochemical properties of MnO2 and their specific merits. Finally, we discuss the future perspectives of MnO2 for SC and ZIB applications regarding the investigation of charge storage mechanisms, materials design and the enhancement of electrochemical performance.