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Abstract:
Ionogels are an attractive class of materials for smart and flexible electronics and are prepared from the combination of a polymer and ionic liquid which is entrapped in this matrix. Ionogels provide a continuous conductive phase with high thermal, mechanical, and chemical stability. However, because of the higher percentage of ionic liquids it is difficult to obtain an ionogel with high ionic conductivity and mechanical stability, which are very important from an application point of view. In this work, ionogel films with high flexibility, excellent ionic conductivity, and exceptional stability were prepared using polyvinyl alcohol as the host polymer matrix and 1-ethyl-3-methylimidazolium hydrogen sulfate as the ionic liquid using water as the solvent for energy storage application. The prepared ionogel films exhibited good mechanical stability along with sustaining strain of more than 100% at room temperature and low temperature, the ability to withstand twisting up to 360° and different bending conditions, and excellent ionic conductivity of 5.12 × 10−3 S/cm. The supercapacitor cell fabricated using the optimized ionogel film showed a capacitance of 39.9 F/g with an energy and power densities of 5.5 Wh/kg and 0.3 kW/kg, respectively confirming the suitability of ionogels for supercapacitor application.

Keywords:
Ionic liquid, Gel polymer electrolyte, Ionic conductivity, 1-Ethyl-3-methylimidazolium hydrogen sulfate, Supercapacitors

Abstract:
This paper provides a comprehensive overview of the influence of 1-Butyl-1-Methylpyrrolidinium Trifluoromethanesulfonate (BMPyrrOTf)-ionic liquid on a new polymer electrolyte where Polyethylene oxide (PEO) as host and ammonium iodide (NH4I) as salt. These IL-doped solid polymer electrolyte were prepared using solution cast technique. Various characterisation techniques have been utilized to evaluate the qualitative and quantitative estimation of polymer electrolyte like Polarized microscopy (POM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Linear sweep voltammetry (LSV), Ionic transference no. (tion) and Impedance spectroscopy. Doping IL increases conductivity and highest achieve at 8 wt% of BMPyrrOTF with conductivity value reaches upto 4.15 × 10–5 S/cm at. Using Wagner’s polarization method, Ionic transference measurement support ionic conduction while stable potential window has further affirmed good electrochemical stability of films. The highest conducting IL-enriched polymer electrolyte sandwiched low-cost dye-sensitized solar cells (DSSCs) and electric double layer capacitors (EDLCs) have been developed, and their performance is conveniently appropriate.

Abstract:
This work reports an easy, straightforward, and cost-effective method to synthesize a composite material using multiwalled carbon nanotubes (MWCNTs) and silver nanoparticles (Ag NPs) for application as an electrode in supercapacitors. The objective of this work was to enhance the charge transfer mechanism in supercapacitor cells by introducing the conductive particles in the MWCNT framework. The pivotal studies, like scanning (SEM), and transmission (TEM) electron microscopy, X-ray diffraction (XRD), Raman, and X-ray photoelectron (XPS) spectroscopy confirmed the formation of the composite as well as a successful deposition of Ag NPs on MWCNT. The surface area of the composite was evaluated by using the N2 adsorption-desorption studies and it was found to be of the order of 358 m2 g−1. Electrochemical studies were performed using a two-electrode system. Magnesium ion-based polymer gel electrolyte was used as an electrolyte material. The single electrode-specific capacitance was observed to be ∼31.9 F g−1 with power density and energy density values of ∼4.4 kW kg−1 and 1.2 Wh kg−1, respectively, at a current density of 0.46 A g−1. The cell was stable up to ∼5000 charge-discharge cycles with ∼96% of capacitance retention at the end of 5000 cycles.

Keywords:
Supercapacitor, Gel polymer electrolyte, MWCNTs

Abstract:
Porous carbons find various applications, including as adsorbents for clean water production and as electrode materials in energy storage devices such as supercapacitors. While supercapacitors reach higher power densities than batteries, they are less widely used, as their energy density is lower. We present a low-temperature wet ultrasonochemical synthesis technique to modify the surface of activated carbon with 1 wt% Cu nanoparticles. We analyzed the modified carbon using X-ray diffraction, Raman spectroscopy, scanning electron microscopy, and transmission electron microscopy and confirmed the composite formation by N2 adsorption–desorption isotherms at 77 K. For comparison, we did the same tests on pristine carbon. We used the modified carbon as an electrode material in a homebuilt supercapacitor filled with gel polymer electrolyte and as an absorbent of Malachite green dye. In both applications, the modified carbon performed substantially better than its pristine counterpart. The modified-carbon supercapacitor exhibited a single electrode-specific capacitance of approximately 68.9 F g1. It also demonstrated an energy density of 9.8 W h kg1 and a power density of 1.4 kW kg1. These values represent improvements over the pristine-carbon supercapacitor, with increases of 25.7 F g1 in capacitance, 3.8 W h kg1 in energy density, and 0.5 kW kg1 in power density. After 10 000 charging–discharging cycles, the capacitance of the modified-carbon supercapacitor decreased by approximately 10%, indicating good durability of the material. We found that the modified carbon’s absorbance capacity for Malachite dye is more than that of the pristine carbon; the adsorption capacity value was B153.16 mg g1 for modified carbon with pseudo-second kinetic order, in accordance with the Redlich–Peterson adsorption model.

Abstract:
The sustainable transformation of bio-waste into usable, material has gained great scientific interest. In this paper, we have presented preparation of an activated carbon material from a natural mushroom (Suillus boletus) and explor its properties for supercapacitor and dye adsorption applications. The produced cell exhibited a single electrode capacitance of ∼247 F g−1 with the energy and power density of ∼35 Wh kg−1 and 1.3 kW kg−1, respectively. The cell worked well for ∼20,000 cycles with ∼30% initial declination in capacitance. Three cells connected in series glowed a 2.0 V LED for ∼1.5 min. Moreover, ultrafast adsorption of methylene blue dye onto the prepared carbon as an adsorbent was recorded with ∼100% removal efficiency in an equilibrium time of three minutes. The performed tests indicate that the mushroom-derived activated carbon has the potential to become a high-performance electrode material for supercapacitors and an adsorbent for real-time wastewater treatment applications.

Keywords:
Activated carbon, Amorphous material, Biomass, Polymer gel electrolyte, Supercapacitor, Dye adsorption

Abstract:
Utilization of CoO@Co3O4-x-Ag (x denotes 1, 3, and 5 wt% of Ag) nanocomposites as supercapacitor electrodes is the main aim of this study. A new low-temperature wet chemical approach is proposed to modify the commercial cobalt oxide material with silver nanoparticle (NP) balls of size 1–5 nm. The structure and morphology of the as-prepared nanocomposites were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and N2 adsorption–desorption measurements. Hydrogels known to be soft but stable structures were used here as perfect carriers for conductive nanoparticles such as carbons. Furthermore, hydrogels with a large amount of water in their network can give more flexibility to the system. Fabrication of an electrochemical cell can be achieved by combining these materials with a layer-by-layer structure. The performance characteristics of the cells were examined by electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and galvanostatic charge discharge (GCD). Cobalt oxide modified with 5 wt% Ag gave the best supercapacitor results, and the cell offers a specific capacitance of ∼38 mF cm−2 in two-electrode configurations.

Abstract:
The electrochemical properties of metal oxides are very attractive and fascinating in general, making them a potential candidate for supercapacitor application. Vanadium oxide is of particular interest because it possesses a variety of valence states and is also cost effective with low toxicity and a wide voltage window. In the present study, vanadium oxide nanorods were synthesized using a modified sol–gel technique at low temperature. Surface morphology and crystallinity studies were carried out by using scanning electron microscopy, transmission electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy analysis. To the best of our knowledge, the as-prepared nanorods were tested with magnesium ion based polymer gel electrolyte for the first time. The prepared supercapacitor cell exhibits high capacitance values of the order of ~ 141.8 F g−1 with power density of ~ 2.3 kW kg−1 and energy density of ~ 19.1 Wh kg−1. The cells show excellent rate capability and good cycling stability.

Abstract:
In the present work, we report the synthesis of surface modified activated carbon (AC). The surface of the activated carbon have been modified by using silver nanoparticles. The synthesis process is simple, cost effective and environment friendly. The modified-AC powders have been characterized by using X-ray diffraction, scanning electron microscopy and surface area and pore size measurements. The electrochemical performance of the prepared materials have been tested by fabricating symmetric configuration of EDLC by using magnesium-ion based polymer electrolytes. The cells have been tested by using cyclic voltammetry, electrochemical impedance spectroscopy and galvanostatic charge-discharge technique. AC with 3 wt% of silver presents best results with specific capacitance of the order of 398 F g−1 energy density and power density of 55 Wh kg−1 and 2.4 kW kg−1 making it an interesting material for supercapacitor application.

Keywords:
supercapacitor, activated carbon-silver composite, gel polymer electrolyte, electrochemical studies

Abstract:
In this work, a facile, wet chemical synthesis was utilized to achieve a series of lithium manganese oxide (LiMn2O4, (LMO) with 1–5%wt. graphene oxide (GO) composites. The average crystallite sizes estimated by the Rietveld method of LMO/GO nanocomposites were in the range of 18–27 nm. The electrochemical performance was studied using CR2013 coin-type cell batteries prepared from pristine LMO material and LMO modified with 5%wt. GO. Synthesized materials were tested as positive electrodes for Li-ion batteries in the voltage range between 3.0 and 4.3 V at room temperature. The specific discharge capacity after 100 cycles for LMO and LMO/5%wt. GO were 84 and 83 mAh g^−1, respectively. The LMO material modified with 5%wt. of graphene oxide flakes retained more than 91% of its initial specific capacity, as compared with the 86% of pristine LMO material.

Keywords:
lithium manganese oxide, LiMn2O4, graphene oxide, cathode material, lithium ion battery

Abstract:
A novel solution combustion synthesis of nanoscale spinel-structured Co3O4 powder was proposed in this work. The obtained material was composed of loosely arranged nanoparticles whose average diameter was about 36 nm. The as-prepared cobalt oxide powder was also tested as the anode material for Li-ion batteries and revealed specific capacities of 1060 and 533 mAh·g^−1 after 100 cycles at charge–discharge current densities of 100 and 500 mA·g^−1, respectively. Moreover, electrochemical measurements indicate that even though the synthesized nanomaterial possesses a low active surface area, it exhibits a relatively high specific capacity measured at 100 mA·g^−1 after 100 cycles and a quite good rate capability at current densities between 50 and 5000 mA·g^−1.

Keywords:
anode material, cobalt oxide, lithium-ion battery, solution combustion synthesis, transition metal oxide

Abstract:
Activated carbons are one of the possible electrode materials for supercapacitors (SCs), which are widely used in commercial applications. Herein, we reported the synthesis of a novel activated carbon derived through a cavitation process from the mixture of native European deciduous trees, Birch, Fagaceae, and Carpinus betulus (commonly known as European hornbeam), which was employed as the electrode material in SC. From the morphological and structural characterization, we observed that the prepared sample is a desirable carbon with good porosity and high specific surface area of about 614 m^2 g^-1. The electrochemical properties of the synthesized material were evaluated with a three-electrode configuration in 1.0 M H2SO4 electrolyte. It was found that in device mode, the carbon material delivers a specific capacitance of 24 F g^-1 at 0.25 A g^-1 with excellent cycling stability of over 10000 consecutive charge/discharge cycles. Thus, our studies demonstrate the facile synthesis of biomass-derived carbon and its application as a versatile electrode material for SC applications.

Keywords:
biomass, carbon material, deciduous trees, electrode material, supercapacitor

Abstract:
In this work, we successfully synthesized series of LiNi0.5Mn1.5O4 (LNMO) cathode materials with spinel structure by using a facile sol-gel method and then calcined at various temperature ranging from 600 to 1000 °C. The application of different calcination temperatures significantly influenced the surface morphology, stoichiometry and crystalline nature of the as-synthesized LNMO material. According to the results of physical characterizations, the LNMO materials calcined at various temperatures mainly revealed the stoichiometric disordered Fd-3m structure with a small amount of well-ordered P4332 phase. The structural analysis also exhibited that the control of the calcination temperature contributed to the higher crystalline nature. Moreover, the morphological investigations indicated that the increasing calcination temperatures caused the formation of large micron-sized LNMO material. In turn, the electrochemical evaluations revealed the impact of the calcination temperatures on enhancing the electrochemical performances of the LNMO electrode materials up to 900 °C. The LNMO electrode calcined at 900 °C exhibited an impressive initial discharge specific capacity of ca. 142 mAh g^−1 between 3.5 and 4.9 V vs. Li/Li+, and remarkably improved capacity retention of 97% over 50 cycles. Those excellent electrochemical properties were associated with the presence of the dominant Fd-3m phase over the P4332 phase. Additionally, the results of the corrosion and dissolution tests which were performed for all calcined LNMO materials in order to estimate the amount of manganese and nickel ions leached from them, proved that the micro-sized LNMO calcined at 900 °C was the most stable.

Keywords:
spinel LiNi0.5Mn1.5O4, sol-gel synthesis, calcination temperature, cathode material, lithium-ion batteries

Abstract:
This work describes a use of a composite nanomaterial which consists of multiwall carbon nanotubes covered by iron oxide nanoparticles as a hybrid electrode in aqueous supercapacitor. The investigated nanomaterial was manufactured in a two-step simple chemical synthesis in which the first step was a functionalization of carbon nanotubes whereas the second one was the deposition of iron oxide. According the morphological and structural characterization, the carbon nanotubes with diameters of 10–40 nm were successfully covered by randomly-dispersed magnetite nanoparticles with average diameter of 10 nm. Moreover, the thermogravimetric analysis results indicated that the mass ratio between carbon nanotubes and iron oxide nanoparticles was about 65–35%. The electrochemical performance of studied hybrid electrode was tested in 1M aqueous KCl electrolyte. The highest specific capacitance of 143 F g^‒1 was recorded at a discharge current density of 1 A g^‒1. The investigated nanomaterial also exhibited excellent cycling stability i.e. 81% retention of the initial capacitance after 3000 cycles.

Keywords:
hybrid electrode, magnetite, multiwall carbon nanotube, nanocomposite, supercapacitor

Keywords:
Supercapacitors, Activated Carbon, Polymer gel electrolyte, Surface modification

Keywords:
Supercapacitors, Polymer gel electrolyte, Host polymer, ELDCs

Keywords:
Supercapacitors, Activated Carbon, Polymer gel electrolyte, Surface modification

Keywords:
Supercapacitors, MWCNTs, Polymer gel electrolyte, Surface modification

Keywords:
Supercapacitors, Activated carbon, Polymer gel electrolyte