Solid-state Symmetric Supercapacitor Research Articles

Engineered nano-architecture for enhanced energy storage capabilities of MoS2/CNT-heterostructures: A potential supercapacitor electrode

Hydrothermal synthesis was utilized to achieve the direct growth of molybdenum disulphide (MoS2) nanoflakes on carbon nanotubes (CNT). Through this method, MoS2/CNT heterostructures with engineered microstructure have been obtained by suitably optimizing the synthesis conditions. Raman, X-ray photoelectron spectroscopy, and electron microscopy have been utilized to characterize the heterostructure. The present study investigated the influence of varying amounts of CNT and MoS2 within the heterostructure on its electrochemical properties. The optimization of the heterostructure morphology has resulted in enhanced electrochemical performance, with a high specific capacitance of ∼436 F/g at 1 A/g, along with good rate capability. The charge storage mechanism was explained by using Dunn's power law. Further, the MoS2/CNT heterostructure was employed to fabricate a solid-state symmetric supercapacitor. The device exhibited a specific capacitance of ∼164 F/g at 1 A/g, along with good cyclic stability, retaining 96 % of its capacitance after 1000 cycles. Additionally, the device demonstrated high energy and power density values of ∼27 Wh/Kg and 603 W/Kg, respectively. The present study indicates that the MoS2/CNT heterostructure holds great promise as an electrode material for high-performance solid-state supercapacitor devices.

A versatile non-precious metal based electrode material endowed by layer-on-layer structure for methanol oxidation and supercapacitor applications

A high-performance non-noble metal-based electrode is the need of the hour to resolve the challenge of huge energy demand. Energy conversion and storage devices are the two ways to tackle this challenge. In this context, porous and non-noble metal-based electrodes NiCo2O4 (NCO), NiCo2O4/NiO (CNO) and NiCo2O4/NiO/rGO (CNOG) are developed as a bifunctional electrode for supercapacitor and methanol fuel cell applications. The binary composite of NiCo2O4 with NiO increases the redox sites and enhances its electrochemical activity. The low conductivity and problem of aggregation of transition metal oxides are overcome by developing a hybrid nanocomposite of NiCo2O4/NiO with reduced graphene oxide (rGO). The layer-on-layer morphology of CNOG, and the interfacial interactions among NiCo2O4 nanoflakes, NiO nanoparticles and rGO nanosheets increase the specific surface area of the hybrid, which leads to enhanced ion penetration into the active sites. CNOG acts as a potential anode catalyst for methanol oxidation with excellent structural stability. It exhibits a high methanol oxidation current density with low onset potential and faster kinetics. Symmetric supercapacitor CNOG//CNOG delivers specific capacitance of 59.4989 F/g, energy and power density of 6.69 Wh/kg and 698 W/kg respectively at 3 M KOH aqueous electrolyte. The solid-state symmetric supercapacitor (SSSC) using PVA/KOH electrolyte allows broader potential window, thereby outperforming the aqueous electrolyte. The SSSC exhibits specific capacitance of 88.8 F/g, energy and power density 20.84 Wh/kg and 1003 W/kg respectively at the same current density.

First report on binder-free boehmite (AlOOH) based prototype, flexible, high-energy and high-power density solid-state symmetric supercapacitor

Supercapacitor has potential to accomplish the world-wide growing demand for clean and sustainable energy. It has virtue of both the battery and the conventional capacitor. The proper selection of electrode material is one of the deterministic factors for the excellent performance of supercapacitor. This work presents the first report on the boehmite phase of a polymorph of earth abundant and inexpensive aluminum based oxy hydroxide for energy storage application. The binder-free synthesis of AlOOH electrode has been carried out by the simple, user-friendly, and low-cost successive ionic layer adsorption and reaction (SILAR) technique at 300 K. The X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, field emission scanning electron microscopy, high-resolution transmission electron microscopy and energy-dispersive X-ray spectroscopy characterizations are performed for the knowledge of crystal structure, chemical bonds, oxidation states, morphology and elements present in the sample, respectively. The electrochemical activities of electrode as well as fabricated solid-state symmetric device are disclosed by cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance spectroscopy. The maximum specific capacitance of 726.5 F g−1 @ 5 mV s−1 has been achieved for AlOOH electrode with ~67 % cyclic stability for 6500 cycles. The assembled device exhibits an excellent specific capacitance of 314 F g−1 @ 5 mV s−1, energy density of 242 Wh Kg−1 and power density of 4701 W Kg−1 with ~80 % stability up to 6500 cycles. The device has ability to glow red, green, blue and white coloured light emitting diodes (LEDs) for 50, 52, 27 and 21 min respectively. Also, the fabricated device is successful for glowing a panel ‘MNNIT’ made up by 56 red coloured LEDs. These results indicate that this work can be beneficial for fulfilling the energy demand of future generation.

Redox additive effects on the electrochemical performance of hydrothermally grown, binder-free CuO nanosheets in aqueous electrolytes

Adding redox additives into the traditional electrolytes is an efficient approach to achieving high-performance binary metal oxide electrode-based supercapacitors (SCs). Herein, binder-free CuO nanosheets are developed on nickel foams via a facile hydrothermal approach, and their charge storage performance in K3[Fe(CN)6] (KFCN) redox additive electrolyte is investigated. In a three-terminal (3T) configuration, the as-prepared electrode demonstrates a remarkable capacitance of 2755 mF cm−2 (2296 F g−1) in KFCN redox additive electrolyte, which is 10 times greater than that obtained in bare KOH electrolyte (266 mF cm−2 or 222 F g−1). Further, the 93 % capacitance retention after 2000 cyclic voltammetry cycles confirms the reasonable stability of the CuO electrode for SCs with redox additives electrolyte. Additionally, the assembled CuO electrodes-based solid state symmetric supercapacitor (SSC) with redox additive gel electrolyte achieves a maximum energy density (Es) of 31.5 Wh kg−1 at a power density (Ps) of 500 W kg−1. Furthermore, red LEDs are operated by the power source of two SSCs connected in the serial mode for 130 sec. This studies imply that utilizing CuO within redox additive electrolytes could present a simple and cost-effective approach for developing high-energy storage supercapacitors.

In-situ growth of Cu nanoparticles-polybenzidine over GO sheets onto graphite sheet as a novel electrode material for fabrication of supercapacitor device

Introducing and use of novel conductive polymers and their composites for use in the supercapacitor industry is very important. In this study, for the first time, the doping of copper nanoparticles on conductive poly benzidine polymer (Cu-PB) deposited on graphene oxide sheets (GO) created on graphite sheets as a result of the anodizing process (AGs) has been introduced as a novel electrode. Cu-PB/GO/AGs electrode was fabricated simply by anodizing the graphite sheet followed by in-situ polymerization of poly benzidine and finally doping copper nanoparticles on the surface of the electrode. The surface morphology and chemical structure of the Cu-PB/GO/AGs electrode were examined by ATR-IR, XRD, EDX, and FE-SEM analysis. The capacitive behavior of the fabricated electrode was evaluated by electrochemical techniques such as cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and electrochemical impedance spectroscopy (EIS) and the results showed that the Cu-PB/GO/AGs electrode has an excellent capacitive capacity of 777.77 F g−1 at 1 A g−1 without ohmic drop in 1 M H2SO4 solution. Finally, the practical application of Cu-PB/GO/AGs electrode was evaluated by fabricating a symmetrical solid-state supercapacitor device and the results showed that fabricate device has 83.02 % cyclic stability after 10,000 charge-discharge cycles and a capacitance of 305.55 F g−1 at 0.5 A g−1 that proven the Cu-PB/GO/AGs electrode is a promising candidate for use in supercapacitor industries.

Electrochemical Performance of Symmetric Solid-State Supercapacitors Based on Carbon Xerogel Electrodes and Solid Polymer Electrolytes.

For the development and optimization of solid-state symmetrical supercapacitors, herein, we propose using carbon-based electrodes and sodium- and lithium-form Aquivion electrolyte membranes, which serve as the separator and electrolyte. Carbon xerogels, synthesized using microwave-assisted sol-gel methodology, with designed and controlled properties were obtained as electrode materials. Commercial activated carbon (YP-50F, "Kuraray Europe" GmbH) was used as the active material for comparison. Notably, the developed solid-state symmetrical supercapacitors provide sufficiently high specific capacitances of 105-110 F g-1 at 0.2 A g-1, along with an energy density of 4.5 Wh kg-1 at 300 W kg-1, and a voltage window of 0-1.2 V in aqueous environments, also demonstrating an excellent cycling stability for up to 10,000 charge/discharge cycles. These results can demonstrate the potential applications of carbon xerogel as the active electrode material and cation exchange membrane as the electrolyte in the development of solid-state supercapacitor devices.

A novel chemical-free porous carbon micro-rods derived from used wooden chopsticks (CS) for solid-state symmetric supercapacitor device

Energy storage application technology is still in its infancy, and carbon-based materials have gained attention in recent years. The finding of low-cost carbon material with controllable characteristics for energy application is quite a complex thing. The major objective of this work is to carbonize used wooden chopsticks at various temperatures in order to create porous carbon materials. Electrochemical studies were tested in 1 M KOH electrolyte assessed by a three-electrode system for supercapacitor application. Among the prepared carbon materials, CS-7 material prepared at 700 °C with a carbon ratio of 88.2 %, demonstrated a high specific capacitance of 184.66 F/g at 0.3 A/g, and the material exhibited an excellent capacitance endurance of 96 % after 10,000 cycles. An asymmetric solid-state supercapacitor was developed for real-time application to study the electrochemical characteristics of the porous carbon material. This study clarifies the creation of complex porous carbon using waste biomass as an energy storage medium.

Medicinal cannabis industry waste for energy storage in symmetric solid-state supercapacitors

The exploitation of the Cannabis sativa L plant in Argentina is limited to its medicinal, therapeutic, or pain relief purposes. These formulations are produced by extracting active compounds from their flowers, which generates leaves and stems as discarded. A considerable number of countries have approved laws for Cannabis medicinal use around the world, encouraging challenging research to find ways to use this residue generated by this new industry. This study proposes valorizing cannabis waste (stems and leaves) by producing and evaluating activated biocarbons as electrode materials for supercapacitors. Cannabis waste were pyrolyzed at 500 °C; then activation conditions were varied from 60 to 180 min; the impregnation ratio was from 1.5 to 4.5 g KOH/g pyrolyzed waste and fixed temperature at 850 °C. Textural properties were evaluated through scanning electron microscopy, infrared spectroscopy, and N2 adsorption/desorption isotherms. The electrochemical characterization was done using an alkaline electrolyte in a three and two-electrode configuration. Cyclic voltammetry, galvanostatic charge and discharge measurements, and electrochemical impedance spectroscopy were performed. Activated biocarbon reached high surface areas over 2500 m2g−1 and adequate porosity development. The best electrochemical performance was obtained at 0.1 Ag−1 achieving 195.83 Fg−1 as specific capacitance, 23.3 KWKg−1, and 54.40 WhKg−1 as power and energy density in the electrode cells. A symmetric solid-state supercapacitor of 2.78 F maximum capacitance at 7.5 mA and 1.2 V potential was developed. These results position activated biocarbon derived from cannabis residues as potential electrode materials in supercapacitors.

Performance of solid-state symmetric supercapacitors based on Dy2S3 electrodes

Rare earth metal sulfides show good capacitance retention and better charge discharge performance. Dysprosium based materials could be a promising candidate for the utilization in supercapacitors due to it's multiple transition states. The dysprosium sulfide (Dy2S3) thin films were deposited on stainless steel (SS) substrate using facile successive ionic layer adsorption and reaction (SILAR) method. The films exhibits orthorhombic crystal structure and spherical nanoparticles morphology. The electrochemical supercapacitive performance of Dy2S3 film showed maximum specific capacitance (Cs) of 273 F g−1 at a scan rate of 5 mV s−1 with excellent (83 %) cycling performance over 2000 cycles in 1 M Na2SO4 electrolyte. The industrial application of SILAR deposited Dy2S3 thin film was examined by fabricating flexible solid-state symmetric supercapacitor (FSS-SSC) device with configuration Dy2S3/PVA-Na2SO4/Dy2S3. It exhibited Cs of 26 F g−1 with specific energy of 17 Wh kg−1 and specific power of 520 W kg−1. A good cyclic stability was observed with capacitive retention of 79 % at the scan rate of 100 mV s−1 after 5000 cyclic voltammetry (CV) cycles. This study highlights the potential application of Dy2S3 for supercapacitor application.

Pseudocapacitive electrode performance of zinc oxide decorated reduced graphene oxide/poly(1,8-diaminonaphthalene) composite

Development of Reduced graphene oxide/Zinc oxide/poly(1,8-diaminonaphthalene) (rGO/ZnO/PDAN) composite and its supercapacitor performance has been evaluated. Functional, crystal and morphological structures along with the thermal stability of the polymer-impregnated composite were studied using analyses such as FTIR, powder XRD, Raman, SEM and TGA techniques. The SEM images showcased the random decoration of irregularly shaped ZnO in between the wrinkled rGO sheets and the PDAN. The defective structure of the hybrid composite contributes capacitive features through electron transfer kinetics. The specific capacitance value for the rGO/ZnO/PDAN composite modified NF electrode in 3 M KOH was found to be 239 F/g at the current density of 0.5 A/g. The capacitance retained is 92 % after 5000 cycles at 5 A/g current density. A solid-state symmetrical supercapacitor device based on a novel rGO/ZnO/PDAN composite was successfully developed, which exhibits the specific capacity (40 at 0.6 A/g), energy density (12.66 Wh/kg) and power density (993 W/kg). The synergistic combination of surface-active nitrogen heteroatoms, extended conjugation and ZnO particles decorated over rGO sheets of rGO/ZnO/PDAN ternary hybrid composite displayed significant structural stability and electrochemical pseudocapacitive performances.

Hard carbon-based electrode boosts the performance of a solid-state symmetric supercapacitor

Hard carbon materials have gained extensive utilization in energy storage systems because of their stable chemical properties, unique lamellar arrangement, and significant interlayer spacing. In this study, we present a novel porous carbon electrode based on hard carbon to enhance the performance of a solid-state symmetric supercapacitor. This electrode was fabricated through an efficient and straightforward synthetic approach using natural asphalt as the precursor. The resulting carbon electrode exhibits remarkable features including a large surface area (2334.48 m2 g−1), a well-distributed pore size (mesopore ratio of 16.04 %), an appropriate oxygen content (18.11 %), and a lamellar structure. As a result, the as-prepared carbon electrode demonstrates a high specific capacitance of 325.82 F g−1 at 0.5 A g−1, along with excellent rate capability, with coulombic efficiency ranging from 99.89 % at 0.5 A g−1 to 98.92 % at 10 A g−1. Moreover, the assembled symmetrical all-solid-state supercapacitor utilizing this electrode achieves an energy density of 18.91 Wh Kg−1, an equivalent series resistance of 0.820 Ω, a relaxation time of 9.0 s, and self-discharge performance lasting up to 72 h. Notably, owing to its large layer spacing (0.391 nm), the electric double layer capacitor contributes as much as 94 %, indicating favorable electrical double layer characteristics. Our work not only showcases a high-performance electrode material but also contributes to the expanded application of hard carbon.

Unification of DAQ-rGO-PEDOT as binder-free ternary nanocomposite electrode for high performance solid-state symmetrical supercapacitor

A high energy density hybrid supercapacitor has been developed from highly π-conjugated 1,4-diaminioanthraquinone covalently bonded to reduced graphene oxide (DAQ:rGO). The drop casting of DAQ:rGO suspension onto nanostructured PEDOT matrixes has enhanced the microstructure/orderliness, higher homogeneity as confirmed by Raman, FE-SEM and HRTEM studies. The high gravimetric capacitance (622.4 F g−1 at 1 A g−1) emerges from extensively porous matrix of nanostructured PEDOT and low band gap of DAQ:rGO evident from a voltage window of -0.2 to 0.8 V facilitating the redox activity of DAQ. In addition, solid-state symmetric supercapacitor based on ternary electrode with free standing PVA-H2SO4 gel electrolyte possesses specific capacitance of 492.5 F g−1 at 1.5 A g−1 with exceptional energy density (68.39 W h kg−1) and excellent cyclic stability (retaining 100% capacitance after 10,000 cycles. The ability of the four devices to illuminate the LED for 120 s manifests utility of the nanocomposite for future microelectronics.

High-Temperature Oxidized Mo2CTx MXene for a High-Performance Supercapacitor.

Molybdenum carbide (Mo2CTx MXene) did not possess suitable properties for supercapacitors. Herein, a short oxidation method of Mo2CTx in air at moderately high temperatures is proposed for fabricating a Mo2C/MoO3 heterostructure. The stability of Mo2CTx in air up to 700 °C and the phase transition at higher temperatures are confirmed. Such a heterostructure is beneficial in reducing the diffusion energy barrier of H+. In the aqueous system, the Mo2C/MoO3 electrode delivers a capacitance of up to 811 F g-1. A fully assembled symmetric solid-state supercapacitor delivers 224 F g-1 with an excellent retention rate of 91.05% after 7500 cycles. Besides, the supercapacitor can work at the low temperature of -60°, showing good low-temperature properties. The approach presented in this work opens a promising way to turn a neglected MXene, assumed to be unsuitable for supercapacitors, into one of the top-performing supercapacitor electrodes.

A green approach for synthesis of an efficient nano pebbles-like BiVO4@C electrode for supercapacitor application

A simple, sustainable, cost-effective, and environmentally benign BiVO4@C electrode is developed via an in-situ bio-mediated green SILAR approach. The optimized synthesis and electrochemical characterization of a BiVO4@C and BiVO4 electrode are reported. The in-situ incorporation of carbon in the BiVO4 (BiVO4@C) was determined by Raman, XPS, and FTIR spectroscopy. The BiVO4@C electrode demonstrates a large specific surface area (106.7 m2 g−1), higher charge storage, superior capacitive performance, longer discharge time, and excellent cycling stability when compared to BiVO4. The flexible solid-state symmetric supercapacitor (SSC) device using BiVO4@C electrode material with PVA/KOH electrolyte gel delivered maximum specific capacitance (Csp) (154.6 F g−1) and energy density of 42.0 Wh kg−1 at a power density of 571.6 W kg−1. Moreover, the symmetric device exhibited cycle stability of 5000 cycles with 97.4 % capacitance retention paving the way for developing sustainable supercapacitors for commercial application.

Evaluation of Fe3O4 incorporated functionalized carbon nanotube self-standing buckypaper as electrodes for solid-state symmetric supercapacitor

Iron (II, III) oxide and carbonaceous materials drawn considerable attention in energy storage owing to their special features. In this study, simple reverse co-precipitation, acid functionalization and vacuum filtration methods adopted to synthesis Fe3O4 nanoparticles of size 11 nm and –COOH acid functionalized multi-wall carbon nanotubes (FMWCNT). And further used them to prepare and optimize Fe3O4 in FMWCNT as 15 wt% and 25 wt% self-standing buckypapers of around 30-μm thickness as electrodes for solid-state symmetric capacitor in the form of coin cell. The results show that 15 wt% and 25 wt% of Fe3O4-FMWCNT buckypapers hybrid nanostructures have Fe3O4 nanoparticles successfully incorporated in FMWCNT. The 25 wt% Fe3O4-FMWCNT electrodes with charge transfer resistance of 140 Ohm showed high areal specific capacitance (Cs) 78.5 mF/cm2 and retained 80 % of its Cs until 800 cycles even at high current density of 1 mA/cm2, scan rate of 100 mV/s whereas 15 wt% Fe3O4-FMWCNT showed low Cs of 47 mF/cm2 and retained 80 % of its Cs over 5000 cycles whereas only FMWCNT show Cs is 36 mF/cm2 with 54 Ohm. Finally, a solid-state symmetric supercapacitor coin cell with self-standing 25 wt% Fe3O4-FMWCNT buckypaper showed an excellent power density of 129.5 mW cm−3 and energy density of 3.6 mWh cm−3 is the innovation of the current work. This is mainly attributed to the combined effect of pseudocapacitive behavior from Fe3O4 by faradaic reaction with additional charge transfer resistance and electric double layer (EDLC) behavior from FMWCNTs by non-faradaic of electronic, ionic transport during charging-discharging. As-made solid-state symmetric supercapacitor appears as a high-performance storage device without extra support of current collectors for practical applications and for fabrication of planar capacitors.

Conducting co-polymer derived N, S co-doped metal-free hierarchical nanoporous carbon for robust electrochemical capacitor

The present investigation reported metal-free hierarchical porous and robust Nitrogen (N), Sulphur (S) co-doped carbon (NS-CoP@C) electrode for supercapacitor application. The NS-CoP@C was synthesized by single-step carbonization and activation of thiourea co-doped aniline-pyrrole co-polymer (CoP). The thiourea acted as a doping as well as activating agent. The data of three different electrode materials PANI-PPy co-polymer (CoP), PANI-PPy co-polymer derived Carbon (CoP@C) and N, S co-doped carbon derived from PANI-PPy co-polymer (NS-CoP@C) are compared in the present report. The electrode materials were initially characterized by various spectroscopic techniques. It is observed that among the three electrode material, NS-CoP@C possess higher specific surface area (SSA), high pore volume and hierarchal porous structure with a better mesopore-to-micropore volume ratio. In a three-electrode system, NS-CoP@C possesses a high specific capacitance of 344.2 F/g @ 0.5A/g. Moreover, NS-CoP@C electrode was used to fabricate an all solid-state (PVA-1 M H2SO4 polymer gel electrolyte) and aqueous (1 M H2SO4 electrolyte) symmetrical supercapacitor devices in the two-electrode system. This NS-CoP@C electrode was used as both positive and negative electrode material in both types of devices. Among them, the solid-state device operates at a wide potential window of 2 V, as a consequence delivering an implausible energy and power density of 45.25 Wh/kg and 1025.64 W/kg while maintaining a capacity retention of 90.1 % even after 8500 charge-discharge cycles. Hence, the excellent performance of conducting PANI-PPy co-polymer-derived N, S co-doped carbon paved new ground for developing an alternative electrode for futuristic energy storage devices.

Comparative study of different metal-organic framework electrodes synthesized using waste PET bottles for supercapacitor applications

The conversion of plastic waste into high-value metal-organic framework (MOF) materials has currently grabbed the attention as an important research area for mitigating environmental and economic issues. Due to their large surface area and high porosity, MOFs have a significant advantage as supercapacitor electrode material. In this study, MOFs (Cu-MOF, Zr-MOF, and Ti-MOF) were produced from plastic wastes (PET bottles) using hydrothermal approach. These MOFs were tested electrochemically in 1 M H2SO4 electrolyte using three-electrode setup. Among them, Cu-MOF (104.8 F/g at 0.5 A/g) showed higher capacitance and increased diffusion contribution (78.4 %) than its counterparts Zr-MOF (70.5 F/g at 0.5 A/g; 70.4 %) and Ti-MOF (55.5 F/g at 0.5 A/g; 67.5 %). Further, solid-state symmetrical supercapacitor devices have been assembled using all the plastic wastes derived MOFs viz. Cu-MOF//Cu-MOF, Zr-MOF//Zr-MOF, and Ti-MOF//Ti-MOF. Among them, Cu-MOF//Cu-MOF symmetric supercapacitor device performed better than the others by rendering energy density of 18.2 Wh/kg at 825 W/kg power density along with a cyclic stability of 87 % after 10,000 charge-discharge cycles. These studies open new avenues to utilize waste PET bottles to synthesize high functional MOFs for next generation supercapacitors.

Enhanced Electrochemical Performance of BiOCl Nanoflower-RGO Based Supercapacitor in the Presence of Redox Additive Electrolyte

Bismuth oxychloride (BiOCl) nanoflowers and bismuth oxychloride/reduced graphene oxide (BiOCl/rGO) composites with different weight percentage were prepared by solvothermal method. BiOCl/rGO hybrids electrode based symmetric solid state supercapacitor was fabricated by sandwiching alkaline polyvinyl alcohol (PVA/KOH) gel electrolyte in presence and absence of potassium iodide (KI). It delivered maximum specific capacitance of 611 F g−1 in presence of PVA/KOH+KI gel electrolytes, increasing by 8.75% compared to the PVA/KOH based supercapacitor. The energy and power density of the supercapacitor in presence of PVA/KOH+KI were reached 21.21 Wh kg−1 and 1.37 kW kg−1 respectively. The supercapacitor exhibits 90% capacitance retention even after 10 000 cycles.

Thermal stability on solid state symmetric supercapacitors with hydrothermally synthesized Cu2CoSnS4 electrodes

The effects of thiourea concentration on crystal phase, morphology, and the elemental composition and electrochemical characteristics (ECs) of hydrothermally synthesized Cu2CoSnS4 (CCTS) electrodes are systematically studied. In a three-terminal (3T) configuration, layered structure morphology with Cu-rich chemical composition-based electrodes exhibits higher ECs than other electrodes. The thermal reliability of devices up to 60℃ is practically validated via temperature-dependent cyclic voltammetry (CV) and galvanostatic charge–discharge (GCD) measurements for single symmetric solid-state supercapacitor (SSC) devices. The maximum of Cp=(251.87 ± 30.56)Fg−1, E=(89.55 ± 10.35)Whkg−1, P=(800 ± 40.32)Wkg−1 and voltage window expanded up to 1.6 V including red LED operation for 6 min are achieved for the serially connected two SSCs at 1Ag−1, indicating that CCTS can be one promising electrode material for SSCs.

Walnut shell derived N, S co-doped activated carbon for solid-state symmetry supercapacitor device

The kernel of the walnut constitutes a nutrient-dense food source. However, the walnut shell is useless and was thrown away. Therefore, as a small initiative towards waste-to-wealth, herein we developed walnut shell-derived highly porous heteroatom (nitrogen and sulfur) doped activated carbon (NS-WAC) via KOH activation and post-processing treatment by thioacetamide (TAA). The NS-WAC exhibits a high specific surface area (SSA) and various particle size distribution (PSD) involving micropores, mesopores, and macropores, conferring substantial supercapacitor advantages. The NS-WAC possesses a significant proportion of mesopores, which can decrease the ion diffusion path length and improve ion transport efficiency. Hence, NS-WAC demonstrates promising electrochemical performance achieving a high gravimetric specific capacitance of 271.4 Fg−1 at 0.5 Ag−1 in 3 M KOH aqueous electrolyte. Furthermore, the solid-state symmetric supercapacitor (SSC) device exhibited a gravimetric specific capacitance of 52 Fg−1 and volumetric specific capacitance of 74.36F cm−3 at a current density of 0.5 Ag−1. This SSC device also exhibited a gravimetric energy density of 23.4 Wh Kg−1 at a power density of 250 W Kg−1 at a current density of 0.5 Ag−1. It showed superior cycle stability of 91.8% after 10,000 cycles at 5 Ag−1.