Coin Cell Supercapacitors Research Articles

High-performance supercapacitor of ZnO-incorporated structurally modified g-C3N4 with circular mesoporous channels attained via a template-free approach

Abstract Here, the superior structural features of graphitic carbon nitride (g-C3N4) in combination with integrated mesoporous channels have been explored for its use as a supercapacitor electrode material. A facile template-free strategy is adopted for the preparation of ZnO-incorporated modified g-C3N4 nanocomposite, where material characterization via x-ray difraction, Fourier transfrom infrared spectroscopy, field-emission scanning electron microscopy, transmission electron microscopy and x-ray photoelectron spectroscopy analysis revealed the presence of structurally modified g-C3N4 having uniform circular mesoporous channels with well-dispersed ZnO with strong Zn–C and Zn–N interactions. The electrical double-layer capacitance together with the pseudocapacitance of the ZnO/g-C3N4 electrode material resulted in improved performance, leading to a specific capacitance of 146.3 F g−1 at a current density of 0.5 A g−1; an increased capacitance is observed in 5000 repeated charge–discharge cycles. A symmetric coin cell supercapacitor fabricated from the material displayed an energy density of 38.8 mWh kg−1 at a power density of 4259 mW kg−1. Additionally, the long life of 6000 cycles (retaining 100% specific capacitance) exhibited by the coin cell supercapacitor further indicates the promising energy storage nature of the ZnO-incorporated modified g-C3N4 mesoporous nanoarchitecture. Real life application of the ZnO/g-C3N4-derived supercapacitor is illustrated by lighting up a green LED with a series connection of four coin cells.

Zinc cobalt sulfide with carbon (graphene oxide and CNT) based nanocomposite as positive electrode for asymmetric coin cell supercapacitors

Abstract The world dependence on portable electronic devices has increased the demand for high-performance energy storage devices. The use of transition metal sulfides as faradaic electrode materials for electrochemical energy storage is rapidly increasing due to their high energy density. Herein Zinc Cobalt Sulfide (ZCS) with graphene oxide (GO) and carbon nanotubes (CNT) were used to create an interconnected ZCS composite network using a solvothermal technique. The materials were characterized by utilizing XRD, FT-Raman, TGA, FESEM/EDX, XPS, and BET. The electrochemical performance of the materials was examined using cyclic voltammetry (CV), galvanostatic charge–discharge (GCD), and electrochemical impedance spectroscopy (EIS). The prepared electrodes exhibited both pseudocapacitor behavior and double-layer capacitor behavior, indicating the hybrid nature. Furthermore, All the electrode ZCS, ZCS/GO, ZCS/CNT, and ZCS/GO/CNT electrodes demonstrated higher capacitance behavior, with values of 420, 551, 585 and 811 F g−1 at 1 A/g. Among these ZCS/GO/CNT electrode exhibits outstanding electrochemical properties, with a notable retention of 81.08% at 10 Ag−1 because Combining ZCS nanoparticles with interconnected GO and CNT provides excellent electronic conductivity and stability. The assembled ZCS/GO/CNT//graphene oxide asymmetric coin cell (ACC) supercapacitor showed a high energy density of 33.3 Wh kg–1 at a power density of 624 W kg–1. The 3D nanostructure of ZCS/GO/CNT/Graphene oxide has great potential for developing foldable energy storage devices.

Fabrication and performance assessment of coin cell supercapacitors with multiwalled carbon nanotube-supported mixed metal oxide nanocomposites and redox additive electrolyte

In the realm of supercapacitor applications, the fabrication of coin cell supercapacitors with superior performances played a crucial role. In this work, an asymmetrical type coin supercapacitor was fabricated with multiwalled carbon nanotube supported mixed metal oxide (CuO/CoO@MWCNT - CCM) nanocomposites (NCs) and potassium ferrocyanide incorporated KOH based redox additive electrolyte (RAE). The synergistic effect and the enhanced conductivity by the mixed metal oxides and MWCNT, respectively, were acted as the performance enhancer for electrode performances. On the other hand, RAE with optimized concentration provided additional redox active sites for superior performances. The combined effect of CCM NCs and RAE, were responsible for the superior performances. CCM NCs were prepared by one-pot hydrothermal technique and characterized. Working electrodes with CCM NCs were fabricated by doctor blade method and evaluated in KOH and RAE. It exhibited 1838.55 Fg−1 of specific capacitance (Csp) in RAE. Assembled asymmetrical supercapacitors with CCM NCs modified working electrode and activated carbon based anode, delivered 123.91 Fg−1 of Csp at 2.75 Ag−1 in RAE. The assembled supercapacitors delivered the highest energy density of 27.53 Wh kg−1 and power density of 1875 W kg−1 in RAE with an impressive 82.89 % of cyclic retention after 5000 GCD cycles. Finally, an asymmetric coin cell supercapacitor (CR2302) was fabricated with CCM NCs and RAE. The fabricated coin cell delivered the charge and discharge capacities of 157.72 and 55.99 mAh g−1, respectively in KOH, whereas these values were significantly improved 172.46 and 126.2 mAh g−1 respectively, in RAE. It proved that the fabricated coin cell supercapacitors performed well in terms of maximum charge and discharge performances in RAE compared to conventional KOH.

Unveiling magnetite metal-organic frameworks for asymmetric pseudo-supercapacitor with high energy density and magnetocapacitance

Utilizing innovative techniques for electrode fabrication and incorporating novel energy storage concepts through external stimuli forces is crucial for enhancing the specific capacity and commercial feasibility of energy storage devices. The performance of supercapacitors hinges on both capacitive behavior, which enhances charge-discharge characteristics and power density, and ion-diffusion behavior, which boosts energy density. This study delves into the impact of external magnetic fields on supercapacitor performance by enhancing pseudo-capacitive behavior through a facile redox pathway and promoting the diffusion coefficient of the electrolyte. We presented magneto-electrophoretic deposition (M-EPD) to apply a high-surface-area zeolitic imidazolate framework (ZIF), which serves as a robust binder-free strategy. Specifically, the Fe3O4-ZIF-67 nanocomposite is uniformly supported on ferromagnetic nickel foam (NF) and demonstrates an impressive specific capacitance of 656.7 F g−1 (328.4 C g−1) at 1 A g−1. In addition, coin cell supercapacitors assembled with Fe3O4-ZIF-67/NF as positive and Fe3O4-ZIF-67-MWCNT/CF as negative electrodes achieve outstanding energy density (103.3 W h kg−1) at a power density of 750 W kg−1, coupled with excellent cycling stability (83.61 % capacity retention) after 10,000 cycles at 20 A g−1. Notably, the cell exhibits superior magnetocapacitance and the highest diffusion coefficient under an external magnetic field of 100 mT. The energy density reaches 163.2 W h kg−1 at a power density of 750 W kg−1, with a coulombic efficiency of 77.7 %. This represents a 1.58-fold enhancement compared to the absence of the magnetic field. The results demonstrated that ferromagnetic coupling between metal−oxygen−metal centers is enhanced via oxygen 2p orbitals, thereby creating a facile pseudocapacitance mechanism. The ZIF-67 shell further regulates the charge-discharge behavior of the electrode through the interplay between diffusive and capacitive mechanisms. This work introduces a promising new approach for preparing high-surface-area MOF-based electrodes and stimuli-responsive, high-performance electrochemical energy storage devices.

Coal-based graphitized activated carbon for solar energy powered supercapacitor IoT applications

Solar cells show promise as energy conversion gadgets, but their extended use is limited by intermittent sunlight. Self-powered solar cell integration with an electrical energy storage system could be one solution to this problem. Therefore, we have developed a coin cell supercapacitor (SC) device based on coal-based graphitized carbon materials and integrated with solar cells to assess its efficiency for energy transformation and storage for practical validity. Supercapacitor carbon electrode was developed from a naturally abundant carbon precursor i.e. low-grade coal using molasses as binder, for the fabrication of high-quality SC devices. The fabricated supercapacitor exhibits a notable 127 F g−1 specific capacitance, maintaining 92 % of its initial value for up to 10,000 charge/discharge cycles at 5 A g−1, and a maximum energy density of 70.57 Wh kg−1 and power density of 2000.17 W kg−1. In order to create a self-sustaining power pack, the SCs (4 V) are integrated with a commercial solar cell (6 V, 750 mAh). Importantly, in the presenceof natural sunlight, the solar-powered as-fabricated supercapacitor bankcan significantly power a commercial IoT module (4–6 V, 600 mAh) demonstrating its potential for successful solar-to-electric energy transformation and storage. The findings demonstrate that solar-powered coal-based SC can be explored as an incredibly rapid future-proof energy storage technology that can help reduce energy demand in the foreseeable future.

Facile preparation of a highly efficient coin cell supercapacitor based on WO3 nanorods

Developing sustainable energy storage devices is challenging for the progress of energy storage applications. Here, nanotechnology represents a strategic route to reduce the amount of used critical materials, while continuing to take advantage of their properties, thanks to the high surface to volume ratio which characterizes nanostructures. WO3 nanostructures represent a promising active material for energy storage applications, thanks to their wide capability of small positive ions (H+ and Li+) intercalation and their high stability in acidic conditions. The coupling between WO3 nanorods and carbon black powder is studied to realize a highly efficient coin cell supercapacitor. The morphology of WO3 nanorods and carbon black is investigated by using a scanning electron microscope, and the energy storage performances were evaluated by performing cycling voltammetry and galvanostatic charge and discharge analysis, thus obtaining promising specific capacitance results (79 and 70 F/g at 5 mV/s and 0.5 A/g respectively). Moreover, the stability of the obtained coin cell was investigated, thus getting good capacity retention over 250 charge-discharge cycles. Energy and power densities were also calculated, obtaining the highest energy density of 39 Wh/kg at a power density of 500 W/kg. The WO3‑carbon black coin cells are used to power a red LED, so demonstrating the viability for practical applications.

Polyacrylonitrile as a binder realizes high-rate activated-carbon-based supercapacitors

Highly polar CN functional groups on polyacrylonitrile (PAN) facilitate strong hydrogen bonding and dipole-dipole interactions with hydroxyl groups on the surfaces of active materials and current collectors. Here we report that the strong interaction between PAN and carbon black (CB) particles facilitates a uniform distribution of CB particles within the electrode and forms a well-connected conductive network on the surface of active material particles. This significantly enhances electron transport within the electrode, offering superior rate performance and cycling stability beyond traditional binders like polyvinylidene fluoride (PVDF). Activated carbon (AC) electrodes containing 7.70 wt.% PAN binder (AC-7.7PAN) deliver areal capacitances over 0.60 F cm⁻2 at a scan rate of 500 mV s⁻1, and exhibits a high gravimetric energy density (Eg) of 26.20 Wh kg⁻1 and high areal energy density (Ea) of 0.33 mWh cm⁻2 at a current density of 1 A g⁻1. An AC-7.7PAN coin-cell supercapacitor maintains up to 62 % of its initial capacitance at a scan rate of 200 mV s⁻1, while a controlled AC-7.7PVDF coin-cell keeps only 37 % under the same conditions. The AC-7.7PAN coin-cell retains 91 % of its capacity even after 50,000 charge/discharge cycles at a constant current of 5 A g⁻1. The ability of PAN to evenly distribute conductive agents might be attractive for other power-type electrochemical electrodes, for which effective electron transport are extremely required.

“Unveiling marigold assembled micro flowers of tungsten oxide towards solid-state flexible pouch and coin cell supercapacitors”

Marigold analogues micro flowers of tungsten oxide (WO3) have been grown in thin film form through simple and cost-effective solution chemistry approach on stainless steel substrate. Aqueous precursor involving WO4-2 ions agglomerated as self-sacrificing template growing initially into the nano-petal, followed by self-assembly; leading to marigold analogues micro flower surface architecture. This enthralling morphology motivated us not only to fabricate supercapacitive electrode but also to design complete solid-state supercapacitor devices in dual configurations: flexible pouch cell and coin cell. Interestingly, both devices even in symmetric configuration yields remarkable potential window of 1.82 V when sandwiched by gel inclusive of Li+ ions dispersed in non-conducting polyvinyl alcohol matrix. Solid-state flexible pouch cell and coin cell delivered specific capacitances of 103.98 ± 3.59 and 30.09 ± 1.03 F/g respectively at a scan rate of 5 mV/s. Assembled electrode, coin-cell and flexible pouch-cells have been well assessed in-depth through specific capacitances using cyclic voltammetry and galvanostatic charge discharge, diffusive and capacitive contributions, mechanical bending tests, electrochemical active surface area, and electrochemical impedance analysis. Practical applicability has been demonstrated for designed flexible pouch cell to run small fan and light emitting diode panel whereas coin cell to run light emitting diode panel.

Investigation of polyaniline electrodeposition on hydrophilic/hydrophobic carbon cloth substrates for symmetric coin cell supercapacitors

Investigation of polyaniline electrodeposition on hydrophilic/hydrophobic carbon cloth substrates for symmetric coin cell supercapacitors

Fabricating high-performance symmetric coin cell supercapacitor using MnO2/CuO/Co3O4 decorated on rGO sheets as electrode material

Supercapacitors show great potential as energy storage devices and could be the ideal choice for enhancing electronic systems. Here the synthesized rGO, MnO2, CuO and Co3O4 were interlaced via the hot-injection method to produce the rGO/MnO2/CuO/Co3O4 (RMCC). Various structural, functional, thermal, morphological and electrochemical characterizations of this nanocomposite RMCC were analyzed. In both 3-electrode and 2-electrode systems, electrochemical experiments were conducted using electrolytes of various pH levels to find out their specific capacitance, energy and power density and the most beneficial electrolyte that could be used for the fabrication of the coin cell supercapacitor was selected. A specific capacitance of 932.358 F g−1 was established, giving rise to an energy density of 204.49 W h kg−1 and highest power density of 2.5 kW kg−1. The cyclic stability of 85.12 % was obtained after 5000 continuous charge-discharge cycles under KOH. The material was then developed into a coin cell supercapacitor, which had the areal specific capacitance, energy and power density of 133.41 F cm−2, 41.67 μW h cm−2 and 0.996 mW cm−2, respectively. Two such coin cells were mounted onto a holder which glowed a red LED for 2.5 days after it was charged.

A comprehensive study of affordable “water-in-salt” electrolytes and their properties

The search for alternative electrolytes has been extremely topical in recent years with the “water-in-salt” electrolyte, especially, lithium bis(trifluoromethanesulfonyl) imide (LiTFSI) coming to the fore in the context of high-voltage electrolytes. However, “water-in-LiTFSI” exhibits ultra-high cost and low ionic transport when compared with the aqueous lithium-halide, -nitrate as well as -sulphate salts (quoted as LiX). This work rediscovered the properties of a “water-in-salt” (LiX electrolytes) made from a variety of concentration from 1 m to saturated conditions. The changes of physical properties e.g., viscosity, pH, conductivity, density, and temperature during mixing were then reported. The electrochemical properties of electrolyte were tested using carbon-based materials (YEC-8A) as a model system (three electrode configuration), and the finding was then expanded to a coin cell supercapacitor for benchmarking the performance per cost unit. It has been found that the use of highly concentrated LiX electrolytes does not always enhance the potential window. LiBr and LiI shown the redox properties while increasing the concentration can speed up the redox process (voltage remains unchanged). Using superconcentrated LiCl can slightly expand the potential window; however, corrosion is the main task to be addressed. Besides, voltage expansion of LiNO3 is found to be approximately 2.2 V, which is comparable to LiTFSI. The breakdown cost of the electrolyte also shows that LiTFSI exhibits the lowest energy density per cost unit (dollars), while LiNO3 provides the most feasible cost in term of power density. We then marked that the electrolytes such as LiBr and LiI can be used as redox additive electrolytes. This work also shows the fundamental insight into the physical and electrochemical properties of LiX for possible alternative use as a cheap “water-in-salt” electrolyte in energy storage apart from LiTFSI.

Carbamide-mediated facile sol-gel synthesis of porous flower-like ZnCo2O4 microspheres for high-performance asymmetric coin cell supercapacitors

The design and development of ultrahigh-performance nanomaterials possessing novel characteristics are needed to achieve reliable energy storage performance. To satisfy the needs, diverse electrode materials are explored. Even though carbon-based materials hold high surface area and conductivity, their specific capacitance value fails to deliver high-performance applications. Therefore, pseudocapacitive transition metal oxide is adopted to overcome these issues. Among all Zinc Cobaltite, a binary transition metal oxide is widely explored owing to its fascinating electrochemical properties. As most of the synthesis of these kinds of materials requires the hydro/solvothermal method, herein, we have proposed the concept of a facile sol-gel method to prepare this class of materials by using Carbamide as both structure director and fuel to achieve the porous flower-like Zinc Cobaltite. The prepared material delivers the notable gravimetric specific capacitance of 513.3 F g−1. Owing to its unique morphology and porous structure, ion channelization is feasible, which will enhance the electrochemical reaction. Constructed asymmetric coin cell supercapacitor showed an extraordinary specific capacitance of 106.5 F g−1 and energy density of 56.2 Wh kg−1, demonstrating an impressive ability to retain 89.6 % of its capacitance after 4000 cycles at a current density of 6 A g−1. Due to the remarkable electrochemical behavior, this work can act as a guiding tool for designing efficient and cost-effective energy storage devices that will hold prodigious potential in commercial energy storage applications.

Zn doping induces rich oxygen vacancies in δ-MnO2 flower-like nanostructures for impressive energy density coin cell supercapacitor

In this work, Zn-doped δ-MnO2 (ZnMO) flower-like nanostructures on carbon fibers are synthesized by one-pot hydrothermal method. It is found that insertion of Zn ions induces oxygen vacancy defects, increase in active sites and conductivity of δ-MnO2 (MO) structure. These features making ZnMO structure an excellent candidate for the fabrication of electrode material for supercapacitors. It has been revealed that ZnMO@CC electrode delivered an enhanced specific capacitance of 667 F g−1 at a current density of 1 A g−1 as compared to the pristine δ-MnO2 and previously reported nanostructures. The developed asymmetric coin cell supercapacitor (ZnMO//AC) obtained a specific capacitance of 116 F g−1 at 1 A g−1 and achieved an outstanding energy density of 71.5 Wh kg−1 at a power density of 1067.1 W kg−1. Moreover, the device retains its initial capacitance of 92 % after 8000 cycles at 8 A g−1. These results suggest that ZnMO could be an emerging electrode material for the fabrication of high-performance supercapacitors for practical applications. This research hunts for new visions for the preparation of MnO2-based material by doping strategy for energy storage applications, especially supercapacitor.

Transforming Disposed Face Masks into S‐Doped Carbon Nanofibers for High Performance Supercapacitors

AbstractThe substantial increase in discarded face masks since the onset of the COVID‐19 pandemic has resulted in extensive environmental pollution from plastic waste. This study presents a novel upcycling method to repurpose disposable face masks into a carbon‐based nanomaterial for use in supercapacitors. The upcycled sample, CSDFM@800, demonstrates very good supercapacitor properties, boasting a high specific capacitance of 234 F g−1 at a current density of 0.5 A g−1. Additionally, the symmetric coin cell supercapacitor constructed from this material exhibits excellent performance, achieving a high energy density of 8.54 Wh kg−1 at a low current density of 0.5 A g−1, and maintaining superior capacitance retention of 96.8 % after 15,000 charge/discharge cycles at a current density of 10 A g−1. Materials characterisation results and electrochemical analysis reveal that this upcycling process not only preserves the carbon nanofiber structure but also introduces highly reactive sulfur as a heteroatom doping element.

Fabrication of NiO@Ni(OH)2/Graphene Nanosheets//Carbon Electrode as Asymmetric Configuration in Coin Cell Supercapacitor

Electrochemical energy storage devices have emerged as a significant concern for contemporary society global and becoming a devices with great performance are in high demand. Supercapacitors are an alternative that is very suitable for use because of their high-power density, environmentally friendly, long-term cycle, safety, and abundance in nature. NiO and Ni(OH)2 nanoparticles have attracted global attention because of their varied application possibilities and advantages such as low toxicity, low cost, high theoretical capacitance, and environmentally friendly properties. NiO was composited with Ni(OH)2 in this study to enhance the supercapacitor device’s specific capacitance, energy density, and power density. The synthesis of NiO@ Ni(OH)2/Graphene electrodes used a blending method with mass variations of NiO (5, 10, 15, 20, 25) % as active material, and then was characterized using XRD to determine phase constituents and crystal size, SEM to determine morphology, FTIR to test functional groups, Cyclic Voltammetry and Galvanotic Charge-Discharge to test electrochemical properties. The asymmetric coin cell with 15% NiO mass in Ni(OH)2@NiO/ Graphene//Activated Carbon composite has the optimum power density and energy density of 327.4 W/kg and 17.1 Wh/kg.

From waste to energy storage: post-consumer waste expanded polystyrene/rGO composite as a high performance self-standing electrode for coin cell supercapacitors.

This research work aims to explore the potential usage of post-consumer waste expanded polystyrene (EPS) for the fabrication of self-standing electrodes by incorporating reduced graphene oxide (rGO) into it via a facile cost-effective mechanical mixing process. The π-π interaction between the expanded polystyrene and rGO is evidenced from FT-IR and Raman analysis. The elevated thermal stability of the EPS/rGO composite from thermogravimetric analysis (TGA) further confirms the interconnection between the rGO and EPS. This π-π stacking interaction between the rGO and the polystyrene molecules present in the polymer matrix enable the composite material to be interconnected throughout which is beneficial for the charge transport process. The symmetric coin cell supercapacitor fabricated using the EPS/rGO composite electrode can be operated with a high operating voltage of 1.6 V in aqueous KOH and Na2SO4 electrolytes. The devices fabricated with KOH and Na2SO4 electrolytes deliver an areal capacitance of 11.9 mF cm-2 and 10 mF cm-2 at the discharge current density of 0.1 mA cm-2. Further, the devices fabricated with the KOH and Na2SO4 electrolytes demonstrated remarkable rate capability of 87.1% and 99.5% after 10 000 continuous charge discharge cycles. This facile method of preparation without consuming energy or polluting the environment is a novel approach which can be scaled-up to large-scale fabrication of self-standing plastic electrodes for low-cost energy storage applications.

Hierarchical porous carbon derived from petroleum coke via one-step chemical activation for the fabrication of a supercapacitor and real time clock application.

The escalating demand for energy requires highly efficient energy storage devices and advanced materials. Low-cost carbon resources and their derivatives have always been a topical research area. Petroleum coke is an abundant and affordable resource that contributes to the scalability and cost effectiveness of carbon materials. Porous carbon derivatives have acquired great attention for energy storage and conversion owing to their large surface area, environmental friendliness, exceptional electrical conductivity, and economic viability. Thus, in this work, we directly synthesized hierarchical porous carbon materials from oil refinery petroleum coke (pet-coke) using a single-step KOH activation method to utilize them for the fabrication of a coin cell supercapacitor for electronic application. The synthesized pet-coke based porous carbon shows a high specific surface area (1108 m2 g-1) and excellent porosity. After conducting extensive electrochemical analysis, it shows promising specific capacitances of 170 and 70 F g-1 in aqueous and organic electrolytes, respectively. Further, a coin cell supercapacitor was fabricated using the pet-coke derived porous carbon in an organic electrolyte with a potential window of 2.7 V, demonstrating superior rate capability and durability. The calculated energy and power density of the fabricated coin cell indicate its favorable supercapacitor application to act as a backup power source for real time clock (RTC) application in electronics.

Surface modification of a biomass-derived self-supported carbon nano network as an emerging platform for advanced field emitter devices and supercapacitor applications.

Herein, a self-supported carbon network is designed through the sole pyrolysis of Carica papaya seeds (biomass) without any activation agent, demonstrating their field emission and supercapacitor applications. The pyrolysis of seeds in an argon atmosphere leads to the formation of interconnected, rod-like structures. Furthermore, the hydrofluoric acid treatment not only removed impurities, but also resulted in the formation of CaF2 nanocrystals with the addition of F-doping. From the field emission studies, the turn-on field values defined at an emission current density of ∼10 μA cm-2 were found to be ∼2.16 and 1.21 V μm-1 for the as-prepared carbon and F-doped carbon, respectively. Notably, F-doped carbon exhibits a high emission current density of ∼9.49 mA cm-2 and has been drawn at an applied electric field of ∼2.29 V μm-1. Supercapacitor studies were carried out to demonstrate the multi-functionality of the prepared materials. The F-doped carbon electrode material exhibits the highest specific capacitance of 234 F g-1 at 0.5 A g-1. To demonstrate the actual supercapacitor application, the HFC//HFC symmetric coin cell supercapacitor device was assembled. The overall multifunctional applicability of the fabricated hybrid structures provides a futuristic approach to field emission and energy storage applications.

An adhesive cellulose nanocrystal-reinforced nanocomposite hydrogel electrolyte for supercapacitor applications

Hydrogel electrolytes were applied in various energy storage devices, including supercapacitors. However, they still suffer from disadvantages such as low mechanical performance and poor adhesion of the interfaces between electrolytes and electrodes. Herein, an adhesive hydrogel electrolyte with promising mechanical strength and electrochemical performance was designed by introducing hydrophobic carbon chains as long-range physical cross-linkers and cellulose nanocrystal (CNC) as biopolymer nano-reinforcement, and soak-loading liquid electrolytes such as KOH into the hydrogel matrix. The hydrogel electrolyte loaded with 1 M KOH demonstrated the best tensile stress of 362.31 kPa and an elongation of 2479 %, and exhibited self-repairability by applying stimuli on the cut interface. The hydrogel electrolyte showed excellent adhesion on various surfaces, including nonconductive and conductive materials such as cardboard, leather, carbon film, and carbon cloth. Regarding electrochemical properties, the hydrogel electrolyte showed the largest conductivity of 0.207 ± 0.005 S/cm when soak-loading in 1 M KOH for 24 h. Moreover, the hydrogel electrolyte exhibited promising electrochemical performance when assembled into coin-cell supercapacitors using free-standing activated carbon sheets as electrodes. A capacitance of 67.31 F/g at 0.05 A/g, and almost 100 % capacitance retention at 0.1 A/g after 2200 cycles was achieved.

Stable Supercapacitors Based on Activated Carbon Prepared from Italian Orange Juice.

The development of efficient energy storage systems is critical in the transition towards sustainable energy solutions. In this context, the present work investigates the viability of using orange juice, as a promising and sustainable precursor, for the synthesis of activated carbon electrodes for supercapacitor technologies. Through the carbonization-activation process and controlling the preparation parameters (KOH ratio and activation time), we have tailored the specific surface area (SSA) and pore size distribution (PSD) of the resulting carbon materials-crucial parameters that support supercapacitive performance. Several spectroscopic, morphological, and electrochemical techniques are used to characterize the obtained carbon materials. In particular, our optimization efforts revealed that a 5:1 KOH ratio with an activation time up to 120 min produced the highest SSA of about 2203 m2/g. Employing these optimal conditions, we fabricated symmetric coin cell supercapacitors using Na2SO4 as the electrolyte, which exhibited interesting specific capacitance (~56 F/g). Durability testing over 5000 cycles sustained the durability of the as-made activated carbon electrodes, suggesting an excellent retention of specific capacitance. This study not only advances the field of energy storage by introducing a renewable material for electrode fabrication but also contributes to the broader goal of waste reduction through the repurposing of food byproducts.