Specific Capacitance Of Supercapacitor Research Articles

Applying machine learning to understand the properties of biomass carbon materials in supercapacitors

Carbon is a fundamental material in developing electrochemical double-layer capacitors (EDLCs), also known as supercapacitors. Many studies have proven the impact of various carbon material properties, such as surface area, pore volume, and chemical surface composition, on the specific capacitance of supercapacitors (EDLCs). However, research endeavors to comprehensively evaluate the contribution of these material properties in correlation with experimental parameters, such as electrolyte concentration, voltage window, and current density, are scarce. This study aimed to employ machine learning algorithms to comprehend the interdependence between the properties of biomass-based carbon and the aforementioned experimental parameters with the capacitance of EDLCs. Four models of the machine learning algorithms were utilized in this study, including linear regression (LR), M5-Rules, Random Tree (RT), and Multi-Layer Perceptron (MLP), to determine the most suitable algorithm for analyzing and predicting the capacitance of EDLCs. The results revealed that the MLP model exhibited the highest determination correlation coefficient (R) of 0.871 with a Mean Absolute Error (MAE) of 45.069 F/g. Besides, the study utilized a machine learning correlation attribute model and observed that the supercapacitor’s surface area and pore volume demonstrated significant correlations with the same correlation ratio of 0.4. In conclusion, these findings emphasize the importance of considering surface area and pore volume in developing and optimizing supercapacitors. Finally, this study adds knowledge in supercapacitors and provides valuable insights for designing and developing high-performance energy storage devices.

Synthesis by adding CTAB and characterization of Ag@CuO@rGO nanocomposite with a novel core-shell crystal sugar structure and its application in supercapacitors.

In this study, we successfully synthesized Ag@CuO@rGO (rGO wrapped around Ag/CuO) nanocomposites using AgNO3, Cu(NO)32, and NaOH as raw materials and particularly treated CTAB as a template by chemical precipitation, hydrothermal synthesis, and subsequent high-temperature calcination processes. In addition, transmission electron microscopy (TEM) images revealed that the prepared products appeared to have a mixed structure. The results indicated that the best choice was CuO wrapped around Ag nanoparticles to form a core-shell crystal structure, and the crystal particles were arranged similarly to form an icing sugar block structure and were tightly wrapped by rGO. Moreover, the electrochemical test results demonstrated that Ag@CuO@rGO composite electrode material exhibited high pseudocapacitance performance; the material had a high specific capacity of 1453 F g-1 at a current density of 2.5 mA cm-2, and the charging and discharging cycles remained constant up to 2000 times, indicating that the introduction of Ag improved the cycling stability and reversibility of the CuO@rGO electrode material and increased its specific capacitance, leading to the increase in the specific capacitance of supercapacitors. Therefore, the above results strongly support the application of Ag@CuO@rGO in optotronic devices.

Effect of chemical treatment of multi-walled carbon nanotubes on the specific capacitance of supercapacitors

To date, the research on carbon nanomaterials has progressed rapidly. More than 400 papers were written in 2021 on the application of carbon nanomaterials in various fields. The high demand for the use of such materials has increased due to a sharp increase in the demand for semiconductor materials and materials for supercapacitor electrodes and other electrical devices. Despite the unique physical properties of carbon nanomaterials, there are limitations to their use. To solve this problem, various methods of modifying the surface, both through chemical interactions and physical adsorption, were proposed. One of these methods is chemical modification. The evaluation of effect of chemical treatment parameters on the properties of carbon nanomaterials is an urgent task due to the fact that the chemistry of the processes is poorly understood. In this work, the effect of concentrated sulfuric and nitric acids on the change of specific surface area, elemental composition, composition of functional groups, and also on the change of specific capacitance was considered. It is believed that both the porosity and the functional groups formed during oxidation contribute to the change in specific capacitance. The specific surface area of all samples decreased on average by a factor of 1.5–3 after the chemical treatment. Different oxygen and sulfur-containing functional groups are observed after the chemical treatment. The highest specific capacitance of the treated carbon nanofibers was 114 F/g.

Influence on Effective and Ineffective Delamination of Mxene (Ti3c2tx) by Tightly Anchoring Tin Oxide Nanocomposite for Boosting the Specific Capacitance of Supercapacitor

Influence on Effective and Ineffective Delamination of Mxene (Ti3c2tx) by Tightly Anchoring Tin Oxide Nanocomposite for Boosting the Specific Capacitance of Supercapacitor

Three-dimensional nitrogen-doped graphene hydrogel-based flexible all-solid-state supercapacitors

In this paper, a three-dimensional nitrogen-doped graphene nano-gel electrolyte (3DNG-PDMA nano-gel) for the preparation of high-performance all-solid-state supercapacitors was studied. Our research shows that the gel electrolyte has a stable three-dimensional network structure and good ionic conductivity (0.0625 S cm−1), and the all-solid-state supercapacitors (SCs) prepared by this gel electrolyte present good electrochemical performance. The specific capacitance of supercapacitor is 187.5 F g−1 under the current density of 1 A g−1. Even at the high power density of 5 kW kg−1, the energy density of supercapacitor can still reach 38 Wh kg−1. After 2500 cycles, the specific capacitance remains 84.1% of the initial value, indicating that the material has good cycle stability. Besides, the gel has high mechanical flexibility, the strain reaches 2409.4% under the stress of 1805.48 kPa, and it has excellent swelling performance with the swelling rate of 706% in 5 h.

High‐performance all‐solid‐state supercapacitor with binder‐free binary transition metal sulfide array as cathode

SummaryTransition metal sulfides show excellent performance in an aqueous supercapacitor. However, all‐solid‐state supercapacitors are attracting more and more interest because of thinner, lighter, and more flexible. Binary sulfides Ni3Co6S8 nanowire arrays (NCS) are directly grown on a nitrogen‐doped carbon foam (NCF) through hydrothermal reaction, which is applied as a binder‐free electrode for all‐solid‐state supercapacitor. The unique needlelike structure assembled by nanosheet effectively increases the utilization efficiency of active materials and promotes electrochemical performance. The NCS‐NCF electrode shows promising application potential for wearable electronic devices due to the flexibility of NCF. A high‐specific capacitance of 243 mAh g−1is delivered by NCS‐NCF electrode, which also exhibits good rate behavior along with outstanding cycle stability. The NCS‐NCF electrode (positive electrode) and NCF electrode (negative electrode) are employed to assemble asymmetric all‐solid‐state supercapacitor. When the high power density is 675 W kg−1, the energy density of supercapacitor reaches the maximum of 28.31 Wh kg−1. The specific capacitance of supercapacitors could maintain 84%, after 10 000 cycles of galvanostatic charge and discharge under 4 A g−1, indicating the potential application of NCS‐NCF electrode as an excellent supercapacitor electrode material in flexible, wearable energy storage systems.

Effects of electrodeposition time on a manganese dioxide supercapacitor

As is well known that the specific capacitance of supercapacitors cannot be improved by increasing the mass of the deposited MnO2 films, which means an appropriate deposition duration is important. In this study, nanobelt-structured MnO2 films were prepared by the electrochemical deposition method under different deposition time to explore the effects of electrodeposition time change on the microstructure and electrochemical properties of this material. Benefiting from the microstructure of the MnO2 films, the transfer properties of the charged electrons and ions were promoted. Meanwhile, a 3D porous nickel foam was chosen as the deposition substrate, which rendered an enhancement of the MnO2 conductivity and the mass of the active material. The enhanced specific capacitance and specific surface area attributed to synergistic reactions. Subsequently, the electrochemical performances of the as-prepared materials were analyzed via cyclic voltammetry (CV), galvanostatic charge–discharge (GCD) and electrochemical impedance spectroscopy (EIS) tests. Results show that the optimum sample deposited for 50 s has a specific capacitance of 291.9 F g−1 at the current density of 1 A g−1 and lowest Rct. However, its electrochemical stability cannot come up to the level of the 300 s sample due to the microstructure change.

Polyaniline/Cu(II) Metal-organic Frameworks Composite for High Performance Supercapacitor Electrode

The specific capacitance of supercapacitors can be benefited by the porosity of the metal-organic frameworks (MOFs). In this study, a nanocomposite of polyaniline-Cu(II) MOFs (PANI/Cu-MOF) was fabricated by a two-step process including chemical polymerization of aniline and room temperature synthesis of Cu–MOFs in the presence of the as-prepared polyaniline. The obtained compounds were characterized by FT-IR, PXRD, SEM, EDAX mapping, and XPS techniques. PXRD patterns revealed the amorphous character of the nanocomposite. FT-IR and EDS-mapping demonstrate the formation of PANI/Cu–MOF nanocomposite. SEM was applied for studying the PANI/Cu-MOF morphology. As demonstrated by CV (cyclic voltammetry), GCD (galvanostatic charge/discharge), and EIS (electrochemical impedance spectroscopy), PANI/Cu-MOF composite shows better capacitive properties compared to the pure Cu-MOF. Furthermore, the results of CVs indicate that the PANI/Cu-MOF composite has a higher capacitance (734 F g−1 at 5 mV s−1) with good electrochemical cycling stability.

Achieving thermally stable supercapacitors with a temperature responsive electrolyte

Thermally stable electrochemical devices are ideal due to their stabilized performance and longer service life at extreme temperatures. However, ageing in supercapacitors, which is caused by generation of heat induced by high voltage, current, temperature, and aided by temperature induced self-accelerating reactions, plague the performance and lead to shortened service life. Poly(N-isopropylacrylamide) (PNIPAM) has been one of the most studied temperature responsive polymers (TRPs) in the past decades; it has a lower critical solution temperature (LCST) around 32 °C. By integrating PNIPAM into aqueous electrolyte, it was found that once LCST is reached, the specific capacitance of supercapacitors is reduced, which is accredited to drag of ion migration and precipitated polymer chains reside upon electrode surface. The capacitance reduction is even more obvious when the electrolyte solute changed into large size solute potassium ferricyanide. In terms of specific capacitance, comparing to an increase of the control, the PNIPAM integrated systems experienced a decrease under 70 °C. The integration of TRPs into electrochemical systems offers alternative approach to suppress high temperature capacitive reactions and ageing, thus could guarantee longer service life, performance stabilized supercapacitors.

(Invited) Nanowire Electrodes for Electrochemical Capacitors and Nanoparticles for Current Conduction

Electrochemical capacitors (ECs) show the improved energy density, somewhat comparable to batteries, with excellent power density. Depending on the charge storage mechanism, ECs can be separated into two types: 1) supercapacitors, 2) pseudocapacitors. Supercapacitors store charges via the formation of the electric double layers at the interfaces of the electrode and electrolyte. In theory, the specific capacitance of supercapacitors can be linearly scaled with the surface area of the electrode. Hence, high-surface-area carbon nanotubes and graphenes are often used for the electrode of supercapacitors to increase the capacitance. The double layer capacitance is, however, intrinsically limited to a low value, typically in a range of 20 μF/cm2 to 50 μF/cm2. To this limitation, redox active substances have been incorporated with the porous electrodes to spuriously increase the capacitance based on their faradaic reaction (i.e. pseudocapacitance). This type of ECs is also known as pseudocapacitors. Thanks to the faradaic reaction, pseudocapacitors show higher energy density than that of supercapacitors. But instead, the power density of pseudocapacitors deteriorates plausibly due to the charge transfer resistance involved in the redox active substances. In developing pseudocapacitors, in most case, the energy density is increased at the expense of the power density. To improve the energy density without sacrificing the power density, a large number of metal oxides and conducting polymers have been recently examined on their morphology and electrochemical properties for the use of the electrode. In the present study, we show that monolithic nanowire array electrodes mediate fast ion and electron transport, allowing for charge/discharge at fast rates. In a typical procedure, we prepare a gold nanowire array electrode by the electrodeposition of Au through the cylindrical pores of the in-house anodic aluminum oxide. The subsequent electropolymerization of pyrrole results in the coaxial nanowires in which polypyrrole is conformally coated with the preformed Au nanowires. Thus prepared coaxial nanowire electrodes are examined with galavanostatic charge/discharge measurement and cyclic voltammetry, showing ideal capacitive behaviors even at high charge/discharge rates. The performance of the coaxial nanowires is further examined with electrochemical impedance spectroscopy. The energy capacity and rate capability of the coaxial Ppy/AuNW based pseudocapacitors will be discussed.

Studies on the equivalent serial resistance of carbon supercapacitor

Equivalent serial resistance (ESR) is a crucial factor to effect on the density of power and energy for supercapacitor. In this work, we studied the influence of internal and external factors, including mechanical pressure, temperature, electrolyte concentration and loaded voltage on the performance parameters, especially on the ESR and specific capacitance for carbon supercapacitor. The results indicate that the ESR is mainly contributed from the interface between electrolyte and electrode. In addition, we found that the ESR can be significantly lowered by mechanical pressures from 11ohm at 0N to 1ohm at 800N by decreasing 90%, and in consequence, the specific capacitance of supercapacitor can be improved dramatically from 19.34F/g to 44.87F/g by increasing 128%. Basing on the model of interface with a diffusion layer, we put forward a reasonable explanation for the variation of ESR and specific capacitance with the four factors of pressure, temperature, electrolyte concentration and loaded voltage.

Precursor-controlled and template-free synthesis of nitrogen-doped carbon nanoparticles for supercapacitors

We describe the synthesis of hierarchical porous nitrogen-doped carbon nanoparticles with high specific surface area and specific capacitance for supercapacitors.

Ionic liquid-functionalized partially exfoliated multiwalled carbon nanotubes for high-performance supercapacitors

Partially exfoliated multiwalled carbon nanotubes (PEMWNTs) have great potential to play a major role in electrochemistry, because they have a combination of unique properties of multiwalled carbon nanotubes (MWNTs) and graphene such as high electrical conductivity, high surface area and porosity. In the present study, we have synthesized partially oxidized MWNTs by Hummers method with modest modification and exfoliated to unravel few of the outer layers. Furthermore, the surface of PEMWNTs was functionalized with an ionic liquid (PEMWNTs/IL). The specific capacitance of supercapacitor, fabricated with PEMWNTs/IL, was found to be 242 F g−1 at 2 A g−1 current density, which is 85% higher than that of PEMWNTs-based supercapacitors. The PEMWNTs/IL supercapacitor gains almost 2-fold improvement in energy density along with good cyclic stability. Nyquist plot clearly suggested that charge transfer resistance is significantly reduced by ionic liquid functionalization, but the electron transfer among PEMWNTs is not affected. The low frequency region of the Nyquist plot suggests the charge storage in the wrinkles and folds of unraveled graphene layers.

High temperature all solid state supercapacitor based on multi-walled carbon nanotubes and poly[2,5 benzimidazole

Supercapacitor containing multi-walled carbon nanotubes (MWCNT) as the electrode material and phosphoric acid-doped poly[2,5 benzimidazole] (ABPBI) as the solid electrolyte and separator membrane has been investigated in a wide temperature range. Supercapacitors with different solid electrolyte concentrations have been fabricated and evaluated for their electrochemical performance. Specific capacitance of supercapacitors at room temperature was found to increase after the first heating cycle. Supercapacitor containing 10 wt.% of solid electrolyte in the electrode shows higher specific capacitance than the supercapacitor with liquid electrolyte. Cyclic voltammetry analysis of supercapacitors indicates high rate capability. The linear increase in the specific capacitance with temperature implies that capacitance is predominantly due to electric double layer. Electrochemical impedance analysis indicates that the mass capacitance and Warburg parameter increase with temperature, while solution resistance and leakage resistance decrease with temperature. The complex capacitance of the supercapacitors shows that both real and loss capacitances increase with temperature. The phase angle of supercapacitors is found to be around 85.2 ± 1° at room temperature and it decreases with temperature. Galvanostatic charge–discharge cycling exhibits almost constant specific capacitance of 28 F g−1 at room temperature. However, it increases sharply and then attains stable value of 52 F g−1 during cycling at 100 °C. The increase in specific capacitance has been attributed to increase in surface area of the carbon nanotube (CNT), due to activation by phosphoric acid and diffusion of free phosphoric acid into the central canal of MWCNT.

All solid supercapacitor based on activated carbon and poly [2,5-benzimidazole] for high temperature application

In the present work, we report high temperature performance of solid electrolyte supercapacitor based on activated carbon (AC) and phosphoric acid doped poly [2,5 benzimidazole] (ABPBI). Supercapacitors with varying concentrations of solid electrolyte in the electrode were fabricated and unit cells were analyzed over a wide temperature range of 27–120 °C. Supercapacitor with AC/ABPBI wt ratio 1.0:0.25 exhibited a specific capacitance of 197 F g −1 at room temperature. To the best of our knowledge, the value reported here is one of the highest for electric double layer supercapacitor with a solid electrolyte. The specific capacitance of supercapacitors having various compositions increased with temperature. The specific capacitance for AC/ABPBI wt ratio 1.0:0.25, capacitance increased to 248 F g −1 at 120 °C. The performance of supercapacitors was also analyzed by electrochemical impedance spectroscopy. The Nyquist plots at room temperature and 100 °C were studied by fitting them using Randles equivalent circuit. Supercapacitor with AC/ABPBI wt ratio 1.0:0.25 showed phase angle of 86.8° at low frequency which indicated excellent capacitive behavior at room temperature. The supercapacitor was found to have good stability during galvanostatic charge–discharge cycling even after repeated heating and cooling.

Hybrid supercapacitors based on polyaniline and activated carbon composite electrode materials

PurposeThe purpose of this paper is to develop feasible composite electrodes with a long cycle life and large specific capacitance and to investigate optimal ratio between aniline and activated carbon materials.Design/methodology/approachPANI/AC composite electrode materials were synthesised by in situ polymerisation of aniline on activated carbon with ammonium persulphate as oxidant. Hybrid supercapacitors are assembled by putting Ni‐MH battery separator between positive and negative electrodes. The electrochemical performances of PANI/AC composite electrode materials and supercapacitors are studied.FindingsThe results show that the optimal ratio between aniline and activated carbon is 1:1.08. The specific capacitance of polyaniline electrode materials is 956 F g−1. The specific capacitance of supercapacitors is 159.37 F g−1. This result could be attributed to the pseudocapacitive effect of Ni(OH)2. What's more, the activated carbon addition reduced the resistance of polymer electrode materials thus improving the cyclic life.Research limitations/implicationsThe supercapacitors can be used in the field of automobiles and can solve the problems of energy shortage and environmental pollutions.Originality/valueA hybrid supercapacitor, which was immersed in alkaline solution, was assembled by putting Ni‐MH battery separator between two electrodes Ni(OH)2 as positive electrode and polyaniline composites as negative electrode. In the case of alkaline solution, the capacitive performance of hybrid supercapacitor was improved and excellent.