Symmetric Supercapacitor Cell Research Articles

Attaining promising efficiency through a Quasi-Solid-State symmetrical supercapacitor and Dye-Sensitized solar cell counter electrode utilizing bifunctional Nitrogen-Doped microporous activated carbon

This study addresses the imperative need for high-performance and sustainable energy storage and conversion technologies by leveraging the unique properties of nitrogen-doped porous carbon (N@WnAC) derived from the waste walnut shells (WnS). In the realm of supercapacitors, the N@WnAC demonstrates remarkable performance in a three-electrode system, showcasing a high specific capacitance value of 276.7 Fg−1 at 1 Ag−1, outstanding stability (96.6 %, 5000 charge–discharge cycles) and favourable rate capability (68.8 % at 10 Ag−1). Moreover, a quasi-solid-state symmetrical supercapacitor (N@WnAC//N@WnAC) is fabricated with PVA/H2SO4 gel electrolyte, underscores outstanding performance by delivering high capacitance (126.2 Fg−1 at 0.5 Ag−1), promising rate capability (71.8 % at 5 Ag−1), favourable long-term stability (93.3 %, 5000 charge–discharge cycles), and faster charge–discharge kinetics compared to conventional counterparts. At the same time, N@WnAC//N@WnAC delivers a high energy density (42.27 Whkg−1 at 0.5 Ag−1) that was retained up to 23.96 Whkg−1 even at 5 Ag−1. Simultaneously, the study explores the potential of N@WnAC as a counter-electrode (CE) in dye-sensitized solar cells (DSSC). The obtained results underscore that unique nitrogen doping enhances the electrocatalytic activity, leading to improved electron transfer kinetics and overall cell performance. Moreover, the N@WnAC CE-based DSSC delivers a promising overall solar-to-electrical conversion efficiency of 5.84 %.

Charge storage mechanism and pseudocapacitance performance of NiO and Ce-doped NiO synthesized via modified combustion technique

Supercapacitors, as promising energy storage devices, have gained significant attention due to their ability to deliver high power and efficient charge storage mechanisms. In this work, we report the synthesis and electrochemical characterization of pristine NiO and Ni1-xCexO (x = 0.01, 0.02, 0.03) nanoparticles using a single-step auto ignition combustion method. Preliminary investigations indicate that Ni1-xCexO (x = 0.02) nanoparticles (2 % Ce doping) exhibit superior specific capacitance compared to other compositions. Therefore, we focused on structural, morphological, and vibrational studies on pristine and 2 % Ce-doped NiO. XPS and BET techniques were explored to assess the electronic state and porosity of the samples. Subsequent electrochemical performance evaluations included Cyclic Voltammetry (CV) at various scan rates, Galvanostatic Charge-Discharge (GCD), and Electrochemical Impedance Spectroscopic (EIS) techniques. From CV at a scan rate of 5 mVs−1, specific capacitance values of 419 Fg-1 and 604 Fg-1 were obtained for pristine and 2 % Ce-doped NiO, respectively. GCD studies revealed a specific capacitance of 381 Fg-1 for 2 % Ce-doped NiO at a current density of 1 Ag-1 and demonstrated capacitance retention of 95.1 % over 3000 GCD cycles for a current density of 4 Ag-1. The symmetric two-electrode supercapacitor cell demonstrates exceptional electrochemical performance, exhibiting a high specific capacitance of 122 Fg-1, an impressive energy density of 8.17 WhKg−1, a power density of 700 WKg-1 at 1 Ag-1, and a remarkable 88 % capacitance retention after 5000 GCD cycles. DFT calculations suggest that Ce doping significantly alters pristine NiO's electronic and structural features due to lattice strain. Our work highlights the enhanced electrochemical performance of 2 % Ce-doped NiO and its potential as a good-quality supercapacitor material.

Interconnected hierarchical 3D porous carbon derived from Saccharum officinarum L. leaf based on the synergistic effect of KOH for high performance supercapacitor

ABSTRACT Porous carbon has continuously been explored based on biomass for green energy storage due to its abundant, renewable, environmentally friendly resource, economical features, and thermal-chemical stability. Therefore, this study aimed to present porous carbon derived from sugarcane or Saccharum officinarum L. leaf as a precursor, achieved through a KOH activation strategy that combines a two-step pyrolysis process. The synthesized material exhibited an interconnected 3D hierarchical structure, a high specific surface area of 752 m2/g, and a carbon purity of 91.38%. Supercapacitor cell electrode had the highest specific capacitance of 471 F/g induced by 0.5 M KOH. Furthermore, in the 1 M H2SO4 electrolyte solution, the symmetrical supercapacitor cell electrodes produced the highest specific energy of 65.55 Wh/Kg at a specific power output of 329 W/Kg. As a result, a sustainable green method was established by using a biomass energy source that is applied as high-performance supercapacitor cell material.

The amorphous porous carbon incorporating 1D-nanofiber as electroactive biomass with integrated pyrolysis for high-performance symmetrical supercapacitors

Supercapacitors widely use electroactive biomass as a carbon electrode for energy conversion and storage. In this research, carbon electrodes were fabricated using Nipah mesocarp (NM) as the base material for symmetric supercapacitor cells. NM sample was physically and chemically activated using KOH 0.5 M and CO2 at varying temperatures of 700 °C, 800 °C, and 900 °C. Physical activation is integrated with the carbonization process in a nitrogen atmosphere. A sample obtained by subjecting CO2 to an activation temperature of 800 °C yields a high purity of 90 % carbon atoms with a 1D superstructure (nanofiber structure), which has a high specific surface area of 676 m2g−1 and a high specific capacitance of 300 Fg−1 at 1 Ag−1. Supercapacitors assembled using NM electroactive biomass can achieve a high power density of 146 W kg−1 and an energy density of 42 Wh kg−1 in a 1 M H2SO4. This electroactive biomass has great potential to be considered as an electrode material for energy storage devices or conversions that are abundantly available in the universe, renewable, and economical.

Self-template synthesis of pitch-based hierarchical porous carbon for high performance supercapacitor in aqueous and ionic liquid electrolytes

Pitch-based hierarchical porous carbons (PHPCs) have been fabricated by means of self-templated method that is adopting metal oxides and metallic salts impurities originate from coal tar pitch (CTP) precursor serve as in-situ hard template along with KOH activation. The porosity properties of PHPCs are significantly influenced by the mass ratio of KOH to pitch. The micro-morphology, hierarchical porosity constituted of co-existing micro-/meso-/macropores, specific surface area, surface elementary composition and electrochemical properties have been comprehensively investigated. It is shown that the high specific surface area (2479 m2 g-1), lay-stacked microstructure, hierarchical porosity characteristic and considerable oxygen-containing functional groups (4.51 a.t %) that synergistically facilitate the electrochemical performance of PHPCs. The electrochemical measurements results exhibit that the gravimetric capacitance for the optimal sample PHPCs-4 is as high as 317 F g-1 at a current density of 0.2 A g-1, with retention of 213 F g-1 even at 10 A g-1 in a three-electrode configuration. In a two-electrode device, the PHPCs-4 based symmetric supercapacitor cell exhibits a specific capacitance of 245 F g-1 at 0.1 A g-1, along with a good rate capability of 75.5% (185 F g-1 at 10 A g-1) and a considerable energy density of 8.51Wh kg-1 at a power density of 50 W kg-1. When tested in EMIMBF4 ionic liquid electrolyte at a cell voltage of 3.5 V, the assembled symmetric supercapacitor cell demonstrates a high energy density of 77 Wh kg-1 at a power density of 175 W kg-1, maintaining 65.3 Wh kg-1 at a current density of 1 A g-1, and 32.1 Wh kg-1 at a high power density of 17500 W kg-1. Furthermore, the specific capacitance of the PHPCs-4 based symmetric supercapacitor retains nearly 100% of its initial value over 5000 cycles in 6M KOH aqueous electrolyte and 91.4 % after 2500 cycles in EMIMBF4 ionic liquid electrolyte. This strategy exploits a novel approach to synthesizing hierarchical porous carbons from coal tar pitch using a self-templating method, offering potential benefits for various applications.

Sustainable graphitic carbon derived from oil palm frond biomass for supercapacitor application: Effect of redox additive and artificial neural network‑based modeling approach

One-step pyrolyzed graphitic carbon (GC) derived from oil palm frond biomass was synthesized at different durations (1, 3, and 5 h) without utilizing of activating agent. The optimum GC-5 h exhibited a honeycomb-like structure (1.9 nm), high carbon content (84 %), graphitic peak at 2θ ∼ 24.2°, and wide pore size (2.17 nm) suitable to accommodate solvated electrolyte ions. Symmetric supercapacitor (SSC) cells with three redox additives (hydroquinone (HQ), ammonium monovanadate (AM), and potassium ferrocyanide (PF)) in H2SO4 electrolyte are tested. The GC-5 h SSC shows a CS of 595F/g in 0.01 M HQ/H2SO4 electrolyte at a current density of 3 A/g. The cell exhibits an energy density (ED) of 22 Wh kg−1 and a power density (PD) of 2,400 W kg−1. It demonstrates a capacitance retention of 93 % after 10,000 cycles. To develop the intricate interactions between the electrode structure, active operating circumstances, and electrochemical performance of the SSC, an artificial neural network (ANN) approach was applied herein. The model uses the Levenberg-Marquart training method, incorporating the Tanh and Purelin activation functions. The data demonstrate that the constructed ANN model can predict the SSC with values that nearly match the experimental data with an MSE of 6.8122 × 10−5 and R of 0.9989.

Unveiling the Supercapacitive Performance of B, P Dual‐Doped Graphene in Triple Redox Additives

AbstractDual heteroatom doping of graphene is currently presumed as more promising for energy storage applications. In addition, the development of energy density with multiple redox additives is paying special attention. Here, we report the fabrication of B, P dual‐doped graphene in three various weight combinations. The formation and the quantity of the prepared samples were investigated by XRD, FT‐IR, EDAX and XPS. The B, P dual‐doped graphene derived from the weight ratio of boron and phosphorus dopant in 1 : 3 has achieved an enriched gravimetric capacitance of 360 F g−1 at 1 A g−1 (1 M H2SO4) and greater than RGO (151 F g−1). The energy density of the fabricated symmetric supercapacitor cell is found to be 50 Wh kg−1 in triple redox additives in 1 M H2SO4 solution which is greater than KI (33 Wh Kg−1) and 1 M H2SO4 alone (5 Wh Kg−1) at 2 A g−1. Also, the same cell delivered an increased stability of 99.7 % of capacitance retained from its initial value after 7000 charge–discharge cycles at 5 A g−1.

Porous α-Fe2O3 Hollow Rods/Reduced Graphene Oxide Composites Templated by MoO3 Nanobelts for High-Performance Supercapacitor Applications.

Porous α-Fe2O3 hollow rods/reduced graphene oxide (α-Fe2O3 HR/RGO) composites with unique morphological characteristics and a high surface area are prepared through a template strategy, which was systematically studied and found to have outstanding supercapacitive properties. When served as active material in a three-electrode setup, the optimized α-Fe2O3 HR/RGO-30, comprised 76.5 wt% α-Fe2O3 and 23.2 wt% RGO, was able to offer the largest specific capacitance of 426.3 F g-1, an excellent rate capability as well as satisfactory cycle life with capacitance retention of 87.7% and Coulombic efficiency of 98.9% after continuously charging/discharging at 10 A g-1 for beyond 10,000 cycles. Such electrochemical behaviors of the α-Fe2O3 HR/RGO-30 electrode can rival or even surpass those of many Fe2O3-based electrodes documented in the previous literature. Later, a symmetric supercapacitor cell of α-Fe2O3 HR/RGO-30//α-Fe2O3 HR/RGO-30 was fabricated. The assembled device offers the maximum energy density of 18.7 Wh kg-1, and also exhibits commendable rate capability, and features stable cycling durability (with capacitance retention of 83.2% together with a Coulombic efficiency of 99.3% after 10,000-cycle charge/discharge at 5 A g-1). These notable electrochemical performances enable the α-Fe2O3 HR/RGO-30 composite to be a high-potential material for advanced energy storage systems.

Solid solution-typed defect concept in forming multivalent cations- and oxygen vacancy-filled MnCo2O4-z spinel bifunctional electrodes for innovative symmetrical supercapacitor

Oxygen vacancies-filled MnCo2O4-z (MCO) nanosheets prepared by a two-step process with varied NH4F content have been investigated. MCO prepared with NH4F at 10 mmol (MCO-10) shows excellent to be used not only for cathode and anode but also for a symmetric supercapacitor cell (SSC). This MCO-10 electrode as a cathode not only reaches a high specific capacitance (Cs) of 7249 F/g at 1 A/g but also performs a high value of 2515 F/g at 1 A/g as an anode. An enlarged SSC of 5 × 5 cm2 is developed. One and five light-emitter-diode (LED) bulbs and commercial 100 F supercapacitor devices are tested to authenticate our reported data. The outstanding performance of nonstoichiometric MCO spinel involving the OH− dipole interaction with oxygen vacancies, chemical redox reaction, multiple cationic valence states, and oxygen vacancies-filled defective structure are all connected with the solid solution-typed defect concept to form bifunctional spinel.

Incorporating Gadolinium Oxide (Gd2O3) as a Rare Earth Metal Oxide in Carbon Nanofiber Skeleton for Supercapacitor Application

AbstractIn this study, we synthesized gadolinium oxide nanoparticles (Gd2O3 NPs) incorporated heteroatom‐doped microporous carbon nanofibers (CNF) to serve as electrode materials for enhancing supercapacitive energy storage. Our primary focus is on elucidating the impact of these hybrid electrode materials on key supercapacitor performance properties such as specific capacitance, specific energy, and specific power. To comprehensively assess the structural and chemical attributes of Gd2O3 NPs‐incorporated heteroatom‐doped microporous CNFs (CNF/Gd2O3) we employed an array of advanced characterization techniques, including scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy (RAMAN), X‐ray diffraction (XRD), and X‐ray photoelectron spectroscopy (XPS). Our research has yielded impressive results, demonstrating a significant increase in supercapacitive performance. Specifically, the CNF/Gd2O3‐1 symmetric supercapacitor cell (SSC) has demonstrated a good specific capacitance of 162.3 F/g and a high specific energy of 8.12 Wh/kg at a specific power of 300 W/kg. These findings could be a new pathway to prepare composite electrodes for use in energy storage applications and promote further development for other rare‐earth nanostructures.

An azo functionalized anthraquinone as organic electrode materials for efficient pseudocapacitors with excellent cycling stability

Organic electrode materials (OEM) are attractive candidates for fabrication of pseudocapacitors (PSCs) to resolve the current problems related to low energy density and lower cycling stability. These problems can be effectively addressed by designing OEM electrode materials for PSC applications. Herein, we report the synthesis of 2,6-bis((E)-(4-hydroxyphenyl)diazenyl)anthracene-9,10-dione (AZOAQ) and utilized for fabrication of AZOAQ/graphene foil (GF) electrode. The two-electrode symmetric supercapacitor (SSC) cell made of the AZOAQ/GF show remarkably higher specific capacitance (Csp), excellent energy and power densities compared to reported OEMs. The SSC device made from AZOAQ/GF achieves specific capacitance (Csp) of 159.12 F g−1 at 0.5 A g−1 current density, remarkable than reported for SCs based on OEMs. The higher conductivity exhibited high energy density of 28.64 Wh kg−1 at power density of 1080.02 W kg−1. The SSC cell also displayed outstanding cycling stability with capacitance retention of 93.22 % after 10,000 galvanostatic charging/discharging (GCD) cycles. Furthermore, considering the simple molecular design for OEM electrode material, the proposed AZOAQ molecule would be an attractive, cheaper molecule for large-scale synthesis and fabricating organic electrodes for different energy storage applications in the future.

Optimization and scalability assessment of supercapacitor electrodes based on hydrothermally grown MoS2 on carbon cloth.

MoS2 is a well-known 2D transition metal dichalcogenide (TMD) with feasibility for energy storage applications due to its eco-friendliness and high electroactive surface area. Electrodes based on MoS2 are typically made by either immobilizing its multiphase nanocomposites, having binders and conductive fillers, or by directly growing the materials on current collectors. In this work, we follow and optimize this latter approach by applying a hydrothermal route to directly synthesize MoS2 nanostructures on carbon cloth (MoS2@CC) hence enabling binder-free current collector electrodes. Raman spectroscopy and electron microscopy analyses confirmed the formation of 2H MoS2 nanosheets with hexagonal structure. The as-prepared electrodes were used to assemble symmetric supercapacitor cells, whose performance were tested in various types of electrolytes. Electrochemical measurements indicate that both precursor concentration and growth time significantly affect the device performance. Under optimized conditions, specific capacitance up to 226 F g-1 (at 1 A g-1 in 6 M KOH) was achieved, with corresponding energy and power densities of 5.1 W h kg-1 and 2.1 W kg-1. The device showed good stability, retaining 85% capacitance after 1000 cycles. Furthermore, the electrodes assessed in PYR14-TFSI showed energy and power densities of up to 26.3 W h kg-1 and 2.0 kW kg-1, respectively, indicating their feasibility not only in aqueous but also in ionic liquid electrolytes. In addition, galvanostatic charge/discharge measurements conducted on devices having footprint sizes from 1 cm2 to 25 cm2 show very similar specific capacitances, which proves scalability and thus the practical relevance of the binder-free electrodes demonstrated in this study.

Surfactants effect on the electrochemical properties of FeSe2 electrode for supercapacitor with first principles insights into quantum capacitance

Nanostructured material like FeSe2 has been synthesized through a simple and cost-effective hydrothermal method. The effect of cationic, non-ionic, and anionic surfactants has been studied on the structural, morphological, and electrochemical properties of FeSe2 electrode material. The FeSe2 electrode material prepared with the assistance of CTAB surfactant displayed a superior specific capacitance value of 401 F g −1 at a scan rate of 10 mV s −1 and 337 F g −1 at a current density of 3.3 A g −1, respectively. The maximum energy density of the symmetric supercapacitor cell fabricated with the same material is evaluated to be 47 Wh kg−1 at a power density of 1667 W kg−1. The addition of the surfactant cetyltrimethylammonium bromide (CTAB) during the synthesis process is found to have a significant impact on the charge storage capability of the material, which is attributed to an increase in active surface area, porosity, reduced crystallite size, and reduced bulk resistance, etc. The real-time use of CTAB-based FeSe2 symmetric cells has been verified via illuminating different voltage light-emitting diodes. Further, the electronic properties and the quantum capacitance of FeSe2 material synthesized without the assistance of any surfactant have been analyzed theoretically using first-principles density functional theory calculations. Acquired results unveil the potential growth of FeSe2 electrode material in energy storage applications.

In-situ synthesis of N, S co-doped electrode material by an environmentally benign method towards designing of high voltage (3.0 V) binder-free sustainable aqueous symmetric supercapacitor

In aqueous electrolyte based symmetric supercapacitor, the decomposition of water to evolve hydrogen and oxygen occurs in relatively lower potential window, thereby, limits its cell voltage and needs to be modified so as to achieve high energy density. This manuscript reports a novel greener approach for an in-situ synthesis of N, S co-doped reduced graphene oxide (N, S co-doped rGO-10/20) nanohybrids as porous electrode material for designing a binder-free and up-scaled mass-loaded (5.0 mg cm−2) high voltage (3.0 V) aqueous symmetric supercapacitor in water-in-salt (WIS), 17 m NaClO4 electrolyte. A fairly rich co-doping/integration of heteroatoms (N (7.2 %) and S (1.5 %)) into the rGO matrix takes place through the formation of C-N, C-S and C-SOx-C bonds. The N, S co-doped rGO-20 nanohybrids in three-electrode system shows the pseudocapacitive behavior with the electrochemical stability of potential window (ESPW) of 3.0 V. In two electrodes set-up, the optimized aqueous symmetric supercapacitor cell (SSC) in WIS shows the superb cell voltage at 3.0 V (highest reported to-date), a fairly high areal energy density@areal power density (0.256 (mWh cm−2)@5.239 (mW cm−2)) at 0.7 A/g with excellent capacitance retention (93.7 %) and Coulombic efficiency (99.3 %) after 20 k cycles. Its energy storage capability is further validated by illumination of 125 white LEDs and 91 green LEDs upon lighting a single SSC for 50 s each and forming the tandem device with high cyclic stability (102 %). Under open circuit, SSC exhibits self-discharge to 2.4 V without any further appreciable discharge till 24 h.

Enhanced energy density of quasi‐solid‐state supercapacitor based on activated carbon electrode derived from honeycomb and gel polymer electrolyte with redox‐additive methylene blue

AbstractIncorporation of redox nature at the electrode‐electrolyte interface is of the current research approach for enhancing the specific capacity as well the energy density of the carbon supercapacitor. In the present studies, symmetric carbon supercapacitor cells are fabricated by using gel polymer electrolytes (GPEs) with and without addition of redox‐additive (MB) and activated carbon (AC) extracted from natural bio‐waste honeycomb (HCAC). The redox‐additive polymeric electrolyte offers high room temperature ionic conductivity (σRT ~ 2.3 × 10−3 S cm−1) and electrochemical stability window of ~1.4 V on the addition of 0.1 g of MB. The HC‐based activated carbon (HCAC) offers high surface area ~ 586 m2 g−1 and dominant meso‐porosity. The performance optimization of the supercapacitor cells are examined by using cyclic voltammetry, charge‐discharge (CD) and electrochemical impedance spectroscopy (EIS) techniques. The supercapacitor with redox‐additive GPE shows the electric double layer features along with faradaic reaction at the electrode‐electrolyte interface, which offers high capacitance ~114 F g−1 and specific energy ~7.76 Wh kg−1 at a power density 0.49 kW kg−1, which is almost ~2.5 times higher than the supercapacitor cell without redox‐additive GPE. Furthermore, the supercapacitor cell with 0.1 g MB redox‐additive based electrolyte shows almost stable capacitance up to 10 000 CD cycles with ~36% initial fading.

Development of Modified Mesoporous Carbon from Palm oil Biomass for Energy Storage Supercapacitor Application

Energy storage system research including battery and supercapacitor devices has been studied to increase efficiency, lower their cost and improve environmental friendliness. Supercapacitor (SC) device offers high transient response and power density which suitable for many applications. The electrodes in supercapacitor device usually produced from highly porous carbon materials. In this study, the modified mesoporous carbon was produced from Palm empty fruit bunch (EFB) biomass. The production of mesoporous carbon was done using a low-temperature hydrothermal carbonization process. The mesoporous carbon from EFB biomass has shown good properties in terms of high surface area and porosity. To improve the electrical conductivity of the carbon the modification by nitrogen doping with ammonium chloride and urea was studied. The effect of different nitrogen sources on surface area and pore properties were reported. The modified mesopore carbon was tested in a symmetrical swagelok supercapacitor cell to evaluate the specific capacitance and efficiency using galvanostatic charge-discharge method. The modified mesoporous carbon with urea doped exhibits the highest specific capacitance of 121 F g-1 at current loading of 0.1 A g-1 in an aqueous 1M H2SO4 electrolyte. The modified mesoporous carbon with urea doped has lower internal resistance due to nitrogen from urea enhance the electronic conductivity of the electrodes and thus increase the supercapacitor performance.

Tailoring potential window of aqueous electrolyte via steric molecular engineering for high voltage supercapacitors

Manufacturing economical and environmentally friendly aqueous electrolytes having a large operating potential is crucial to accomplish safe, high-energy and long-life supercapacitors. An emerging approach of superconcentrated Water-in-Salt (WIS) electrolyte significantly improves the performance through a stable, improved thermodynamic potential of water by reducing the free water molecules in the electrolyte. However, this approach raises concern about the cost and toxicity. By the way, we have achieved a similar performance by creating a hydrogen bonding network through the incorporation of additive with electrolyte, which suppresses the water electrolysis even at low salt concentration. This work demonstrates a hydrogen bond constructed electrolyte (Steric effect) using the additive to reduce water activity. In that way, it delivered an extensive operational voltage (>2.3 V) to the electrolyte at a low salt concentration (5M NaClO4). Further, the carbon-based symmetric supercapacitor cell with this electrolyte delivered a capacitance of 112 mF with good capacitance retention (71.4%) after 50,000 cycles. Further, the cell showed its excellency via a low self-discharge rate and leakage current. The performance of the coin cell-type supercapacitor is evaluated as per IEC standards and as well as the traditional method and compared with superconcentrated Water-in-Salt NaClO4. This work opens up new direction for designing high-voltage water-based electrolyte for inexpensive and very stable energy storage devices.

Flexible Polymer-Ionic Liquid Films for Supercapacitor Applications

Mechanically and thermally stable novel gel polymer electrolytes (GPEs) have been prepared and applied in supercapacitor cells. Quasi-solid and flexible films were prepared by solution casting technique and formulated by immobilization of ionic liquids (ILs) differing in their aggregate state. A crosslinking agent and a radical initiator were added to further stabilize them. The physicochemical characteristics of the obtained crosslinked films show that the realized cross-linked structure contributes to their improved mechanical and thermal stability, as well as an order of magnitude higher conductivity than that of the non-crosslinked ones. The obtained GPEs were electrochemically tested as separator in symmetric and hybrid supercapacitor cells and showed good and stable performance in the investigated systems. The crosslinked film is suitable for use as both separator and electrolyte and is promising for the development of high-temperature solid-state supercapacitors with improved capacitance characteristics.

Electrochemical performance of supercapacitor electrodes based on carbon aerogel-reinforced spread tow carbon fiber fabrics

Fabric-based supercapacitor electrodes were fabricated by embedding spread tow carbon fiber fabrics, in monolithic, bicontinuous carbon aerogels (CAG). The incorporation of CAG, at less than 30 wt%, increased the specific surface area of the CAG-CF fabric to above 230 m2 g−1 and the pore volume to about 0.35 cm3 g−1, orders of magnitude higher than that for the as-received carbon fibres. The presence of the CAG not only improves the electrochemical performance of the composite electrodes but may enhance the mechanical response due to the high stiffness of the aerogel structure. Cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance measurements were performed on symmetric supercapacitor cells consisting of two CAG-reinforced fabrics in an ionic liquid electrolyte. The specific capacitance of the symmetric supercapacitor was determined to be in the range 3–5 F g−1, considerably higher than that for the plain carbon fibers. Since optimum structural electrolytes are not yet available, this value was normalized to the total mass of both electrodes to place an upper bound on future structural supercapacitors using this spread tow CAG-CF system. The maximum specific energy and specific power, normalized to the total mass of the electrodes, were around 2.64 W h kg−1 and 0.44 kW kg−1, respectively. These performance metrics demonstrate that the thin CAG-modified spread tow fabrics are promising electrodes for future use in structural supercapacitors. In principle, in future devices, the reduced ply thickness offers both improved mechanical properties and shorter ion diffusion distance, as well as opportunities to fabricate higher voltage multicell assemblies within a given component geometry.

One-step strategy of 3D hierarchical porous carbon with self-heteroatom-doped derived bread waste for high-performance supercapacitor

Bio-waste is a promising carbon source that can be used as a basic component in renewable supercapacitors due to its abundant hierarchical pore structure potential, heteroatom self-doping capability, high surface area, as well as well-defined chemical and mechanical stability. This study converted bread bio-waste into rich 3D hierarchical porous carbon through a one-step facile strategy to be used as the main component of a supercapacitor. The porous carbon was obtained through physical activation approach at different temperatures of 750, 800, 850, and 900 °C without being combined with chemical activation. The optimized activated carbon illustrated high porosity behavior with an abundant 3D hierarchical pore structure consisting of 76.98% micropores and 23.02% mesopores and also produced a well-defined wettability of self-doping heteroatoms. Moreover, the electrochemical behavior in a symmetric supercapacitor cell showed a high specific capacitance of 202 F g−1 at 1 A g−1 with a rate capability of 73% at 10 mV s−1 in a 1 M H2SO4 electrolyte. It was also discovered that the activation temperature of 850 produced the highest energy density of 11.61 Wh kg−1 at a power density of 156.71 W kg−1 with a low equivalent series resistance of 0.11 Ω. Finally, the proof-of-concept showed that bread waste has immense potential as a 3D hierarchical porous carbon source after the synthesis through a single-stage facile approach and can be used as a major renewable electrode component for sustainable supercapacitors.