Aqueous Symmetric Supercapacitor Research Articles

Covalent Organic Framework Derived Oxygen/Sulfur-Doped Porous Carbon for Robust High-Capacitance Symmetric Supercapacitors.

Heteroatom-doped porous carbons (HPCs) have been considered promising electrode materials for supercapacitors due to their improvement of energy density by providing extra pseudocapacity. Covalent organic frameworks (COFs) are obtaining great importance in energy storage because of their designable structure and versatile functionality. Herein, we designed and fabricated oxygen and sulfur dual-doped covalent organic framework (COF) derived HPCs with very high heteroatoms content (up to 25.76 atom%) via a facile coupling reaction. The optimized HPCs exhibit a porous structure with high specific surface area (up to 2835 m2 g-1) along with a high specific capacitance (430 F g-1 at 0.5 A g-1), excellent capacitance retention (96.9%), and high coulombic efficiency (98.5%) after 10000 cycles at 5 A g-1. As electrodes for aqueous symmetric supercapacitors, the HPCs exhibits a high energy density of 60 Wh kg-1 at a 250 W kg-1 power density, excellent cycling stability of capacity retention (82.2%) and a high coulombic efficiency (92.3%) after 10000 cycles at 10 A g-1, indicating attractive application potential in chemical energy storage. This work establishes a promising strategy for preparation of high heteroatom content HPCs using COFs and demonstrates great potential for energy storage/conversion devices.

Effects of Co-doping on the microstructure and electrochemical performance of nickel vanadate (Ni3V2O8) electrode material for aqueous symmetric supercapacitor

Recently, there has been an increased focus on supercapacitors due to their reliable electrochemical energy storage capabilities. This study utilized an environmentally friendly facile hydrothermal method to prepare the nickel vanadate (NiVO) and cobalt-doped nickel vanadate (Co-doped Ni3V2O8) composite for supercapacitor applications. The prepared materials of pure and Co-doped Ni3V2O8 with different concentrations of Co (10 % and 15 %) were evaluated through three electrode assemblies. It is significant to note that although Co smoothed the surface of NiVO, most of the nickel vanadate crystals broke apart into tiny particles and increased the number of electroactive sites. Pure NiVO has a specific capacitance (Cs) of 1638.06 F/g at 5 mV/s. It has been observed that the electrochemical performance has been improved by adding Co 10 % and 15 % in NiVO. The 15 % Co-doped NiVO exhibits an outstanding Cs of 2641.99 F/g at a scan rate of 5 mV/s with a high capacitance retention of 98.14 % after 1k charge-discharges cycles. This excellent performance of the material is due to more electroactive sites and synergistic effects among Co and Ni in the composite. To further elaborate the electrochemical performance of 15 % Co-doped NiVO, it is employed for the fabrication of a symmetries supercapacitor (SSC) device, which shows that the fabricated device has a capacitance of 286 F/g at a current density (CD) of 0.5 A/g and high energy density of 39.7 Wh/kg at a power density of 333.33 W/kg. The symmetric device maintains a cyclic stability of 93.8 % while undergoing 5000 consecutive charge–discharge cycles at a current density of 10 A/g. Based on rigorous testing and analysis, these findings suggest that the prepared electrode material is reliable and suitable for implementation in forthcoming wearable electronic systems.

Role of Nitrogen-doping in porous carbon for enlarging working voltage window of aqueous supercapacitors in neutral electrolyte

The fundamental mechanism on enlarging working voltage window of carbon-based aqueous supercapacitors is still unclear owing to the indistinct principles in inhibiting water splitting occurred at the electrochemical interface. Herein, we design a set of N, O co-doped porous carbon (NOPC) free-standing electrodes with adjustable N-doping level, and establish that N-doping (N-content and specific N-configuration) governs neutral HER and OER. The NOPC electrode with a lower N-doping level can possess a wide working potential window of − 1–1 V, and thus the corresponding aqueous symmetric supercapacitors showcase a wide working voltage window of 2 V in LiCl aqueous solution. In situ spectroscopy evidences and theoretical simulation demonstrate that the low N-doping (N-content and percentage of pyrrolic nitrogen) level can weaken the interaction between the electrode and interfacial water molecules and suppress the formation of *OOH intermediate during the charge–discharge process, and thus significantly decreasing the HER and OER activities to inhibit water splitting. The finding can shed light on the fundamental understanding of mechanism on enlarging working voltage window of carbon-based aqueous supercapacitor.

Morphologically tuned MnO2 thin film electrodes prepared by growth kinetic dependent SILAR approach for high-performance extrinsic pseudocapacitors

Rationally designed electrode materials that are morphologically tuned to attain large surface area can significantly possess the extrinsic pseudocapacitive charge-storing ability. Therefore, the current work approach focuses on synthesizing binder-free MnO2 thin film electrodes with tuned morphology by the SILAR method through alteration in growth kinetics. The growth kinetics of SILAR are controlled by altering the precursor concentrations ratio among metal precursor (MnCl2) and oxidizing agent (KMnO4). The structural analysis confirmed the preparation of the δ-MnO2 phase of manganese oxide. Moreover, alteration in growth kinetics resulted in a change in surface morphology with reduced nanowire size of marigold-like δ-MnO2 microflowers. The MO-3 thin film electrode prepared at an optimum KMnO4 and MnCl2 precursor concentration ratio of 2:1 provides the maximum extrinsic pseudocapacitive conduct with the maximum specific capacitance of 774.5 F g−1. Furthermore, the aqueous symmetric supercapacitor device exhibits the highest specific capacitance of 106 F g−1 with a specific energy of 14.8 Wh kg−1 at a high specific power of 1792 W kg−1 and exhibits 83.2 % capacitive retention over 10,000 cycles. Furthermore, the symmetric aqueous device (MO-3//Na2SO4//MO-3) lights 5 red LEDs, demonstrating its commercial viability for energy storage systems. This research facilitated the scalable synthesis of binder-free δ-MnO2 fine film electrodes with a desired morphology by facile SILAR method, ensuring their practical applicability in symmetric extrinsic pseudocapacitor devices.

Natural N/O/S co-doped defect-rich functional carbon materials for aqueous supercapacitors: Effect mechanism of N-containing functional groups on chemical activation

The efficient synthesis of porous carbons with a micro-mesoporous composite structure from low-cost, multi-source biomass was of significant importance for the fabrication of carbon-based supercapacitors. A novel method for the preparation of micro-mesoporous composite carbon materials by co-pyrolysis of multi-source biomass coupled with KOH activation was proposed in this study. The N, O and S co-doped micro-mesoporous composite carbon materials were synthesized using the bamboo and spiral algae as the precursors and KOH as the activator. Spiral algae, as the main source of heteroatoms, played multiple roles (pore forming agent, dopant and enhancer) in the co-pyrolysis process. The enhanced effect of heteroatom doping on KOH activation facilitated the formation of microporous structures. The KCA-500–2 exhibited a porous structure dominated by micropores, with a specific surface area (SSA) of 2421.85 m2/g. At 0.5 A/g, KCA-500–2 displayed an excellent capacitance of 460F/g and outstanding rate performance (73.5 %). The assembled aqueous symmetric supercapacitor (KCA//KCA) demonstrated a maximum energy density of 19.09 Wh/kg at a power density of 150 W/kg. In addition, KCA//KCA attained 97.96 % capacitance retention after 9,000 cycles. This work revealed the synergistic mechanism between N-containing functional groups and KOH activation, suggesting a theoretical guidance for the synthesis of high-performance supercapacitors.

Dense graphene composite hydrogels as advanced electrode materials for high-performance supercapacitors

In this work, alanine functionalized nanocellulose/graphene composite hydrogels (NCGHalas) were prepared via an easy hydrothermal reaction using alanine, GO, and nanocellulose as reactant. Thanks to this synthesis strategy, NCGHalas exhibited large bulk density, abundant heteroatom functional groups, reasonable porous structure and moderate specific surface area. Based on the above characteristics, the aqueous symmetric supercapacitors (ASSC) assembled by NCGHala25 presented high gravimetric and volumetric specific capacitance of 276.5 F g−1 and 320.8 F cm−3 at 0.3 A g−1, excellent rate performance (77.9 % at 10 A g−1), and long working life of 95.4 % retention after 10,000 cycles at 10 A g−1. Furthermore, the NCGHala25 based ASSC also exhibited large gravimetric and volumetric specific energy densities of 9.6 Wh kg−1 and 11.1 Wh L−1. More importantly, the flexible solid-state supercapacitors (FSSC) fabricated by NCGHala25 and PVA-KOH electrolyte delivered high specific capacitance (178.2 F g−1, 0.3 A g−1), and this value can be maintained for 74.2 % even at 10 A g−1.

An aqueous symmetric supercapacitor with wide window and high energy density using redox electrode of Cu-Al-layered double hydroxides and λ-manganese dioxide.

Manganese oxide is a potential agent in the field of energy storage owing to its changeable redox characteristics, high theoretical specific capacitance and valence shells for charge transfer. On the other hand, due to huge surface area, affordability, customisable composition, layered structure and high theoretical specific capacitance, layered double hydroxides, or LDHs, have drawn a lot of interest. This study employs a three-electrode setup to investigate the supercapacitive performance of λ-manganese dioxide/Cu-Al LDH composite at different compositional ratios. To enhance the adhesive and conductivity capabilities, 10% of CNT additive and PVDF binder are added for the composites. Out of all the composites, the one with the greatest weight percentage of λ-manganese dioxide shows the best electrode performance with a superior specific capacitance of 164 F/g at a scan rate of 10mV/s. Additionally, using a symmetrical two-electrode setup, the best-performing electrode is examined. The result shows an exceptional potential window of 2.7V in a basic electrolyte, a power density of 4.04kW/kg at 3 A/g, an energy density of 20.32 Wh/kg at 1 A/g, and a specific capacitance of 37 F/g.

Electrochemical deposition of NiO/NiCo2O4 nanostructures for high-performance supercapacitors

NiO is widely used in supercapacitors because of its low toxicity, low price and environmental friendliness. In this study, NiO/NiCo2O4 composites were prepared on nickel foam substrates using a simple electrochemical deposition technique. By adjusting the deposition time in the electrochemical parameters, the optimum conditions for the deposition process can be fine-tuned. Characterization techniques such as scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD) confirmed the synthesis of NiO/NiCo2O4 composites. The electrochemical properties of the composite electrode NiO/NiCo2O4/NF were evaluated by cyclic voltammetry (CV), electrostatic charge-discharge (GCD), and electrochemical impedance spectroscopy (EIS). The specific capacitance (Cs) of the prepared composite electrode NiO/NiCo2O4/NF electrode was 717.8 mF/cm2 at 2 mA/cm2 with a capacitance retention of 74.8 %. In addition, Aqueous symmetric supercapacitors (SSCs) and all-solid symmetric supercapacitors were assembled based on the composite NiO/NiCo2O4/NF electrode, respectively. The aqueous SSCs have a power density of 880 μW/cm2 and an energy density of 123.0 μWh/cm2, the all-solid symmetric supercapacitors have a power density of 960 μW/cm2 and an energy density of 24.27 μWh/cm2. The series connection of two identical capacitors can light up light-emitting diodes (LEDs). This research presents a promising technique for producing Ni-based electrode material for supercapacitors.

Application of N/P-rGO composite electrode materials and novel electrolytes in high-performance supercapacitors

Traditional graphene-based electrode materials often can not have excellent gravimetric and volumetric electrochemical properties at the same time. Furthermore, the gel electrolyte widely used at present has the disadvantages of poor water retention, easy solidification, low ionic conductivity, and narrow working temperature range during the working process. In this paper, nanocellulose/N, P co-doped reduced graphene oxide composites (NC-NPrGOs) were synthesized via a simple approach using graphene oxide (GO), ammonium dihydrogen phosphate, and nanocellulose (NC) as raw materials. Meanwhile, a new type of gel electrolyte (SNG) with renewable, wide working temperature range and ultra-high water retention properties was prepared using sodium alginate (SA), NC, GO, and potassium hydroxide as precursors. Benefiting from the unique physical and chemical properties of NC-NPrGOs, the assembled aqueous symmetric supercapacitors assembled by NC-NPrGOs present high gravimetric (303.9 F/g) and volumetric specific capacitance (416.5 F cm−3), large gravimetric (10.5 Wh kg−1) and volumetric energy density (14.6 Wh/L). Due to the multiple interactions of several components in SNG, the flexible solid-state supercapacitors (ASSC) assembled by NC-NPrGO55 and SNG deliver high specific capacitance (240.0 F/g), ultra-long cycling life, excellent bending resistance, a wide range of operating temperatures, and good regenerative performance. In summary, NC-NPrGOs and SNGs are ideal for the investigation of new energy storage devices.

Biomass waste derived from cassia fistula into value-added porous carbon electrode for aqueous symmetric supercapacitors

Activated carbon derived from biomass sources has been renowned as one of the key materials and economical precursors for numerous energy conversion and storage applications. Herein, we utilized a less explored Cassia fistula (Pulp and seed) biomass as the carbon source for supercapacitor application. Further, a less toxic and low activation method has been implemented to activate the biomass-derived carbon. The highly dense seed resulted in better porous compared to the pulp source. The electrochemical performances of the bio-carbon electrodes have been examined by CV, GCD, and EIS studies. The activated carbon derived from the Cassia fistula seed (CFSA) electrode achieved a specific capacitance value of 136.5 Fg−1 at 0.5 Ag−1 in 3 M KOH. Moreover, the electrode demonstrates an extremely long stability by sustaining 98 % of initial capacitance after 10,000 cycles, which signifies the robust electrochemical stability behavior of the obtained electrode. Further, the aqueous symmetric supercapacitor achieved a maximum energy and power density of 7.2 WhKg−1 and 3488.1 WKg−1, respectively. Likewise, after 10,000 stability cycles, the cell retains 96.4 % capacitance at 5 Ag−1 which denotes the noteworthy capacitive behaviour of the CFSA electrode. Thus, the present work suggests an eco-friendly resource for developing an effectual carbon electrode for energy storage applications.

Kenaf-based activated carbon: A sustainable solution for high-performance aqueous symmetric supercapacitors

This study presents an innovative method for synthesizing activated carbon with an exceptionally high surface area (3359 m2 g−1) using kenaf fiber-based biochar through chemical activation. The achieved specific surface area surpasses activated carbon derived from other reported fiber-based precursors. The resulting activated carbon was investigated as electrodes for supercapacitors, revealing a remarkable maximum capacitance of 312 F g−1 at a current density of 0.5 A g−1. An aqueous symmetric supercapacitor employing these high-surface-area electrodes exhibited an outstanding energy density of 18.9 Wh kg−1 at a power density of 250 W kg−1. Notably, the supercapacitor retained exceptional capacitance, maintaining 93% of its initial capacitance even after 5000 charge-discharge cycles.

Mechanochemically Assisted Microwave-Induced Plasma Synthesis of a N-Doped Graphitic Porous Carbon-Based Aqueous Symmetric Supercapacitor with Ultrahigh Volumetric Capacitance and Energy Density

Mechanochemically Assisted Microwave-Induced Plasma Synthesis of a N-Doped Graphitic Porous Carbon-Based Aqueous Symmetric Supercapacitor with Ultrahigh Volumetric Capacitance and Energy Density

Symmetric supercapacitor based on biosynthesized nanosheets of reduced graphene oxide (rGO): Characterization and electrochemical behavior

Reduced graphene oxide (rGO) nanosheets (NS) were synthesized via a simple, rapid, eco-friendly and cost effective biosynthesis approach using Lonar lake isolated bacterium strain Bacillus cabrialesii RIRD-SK (MCC 4670). The biologically prepared rGO nanosheets were characterized via X-ray detection diffraction (XRD), Fourier transform infrared spectrum (FTIR), Raman spectroscopy, Field emission scanning electron microscopy (FE-SEM), Energy dispersive X-ray spectroscopy (EDX), and Brunauer-Emmett-Teller (BET) techniques, respectively. Electrochemical investigation was carried out using the cyclic voltammetry (CV), galvanostatic charge–discharge (GCD) and electrochemical impedance spectroscopy (EIS) tests. Most of the oxygen functional groups species in rGO were successfully eliminated resulting in little (0.39 Ω) charge transfer resistance (Rct). The rGO electrode exhibited 457 F/g specific capacitance at scan rate 5 mV s−1 in 1 M Na2SO4 aqueous electrolyte within the potential window of −1 to 0 V. It showed a superior electrochemical cycle stability of 96 % after 10,000 cyclic voltammetry cycles. The aqueous symmetric supercapacitor device was prepared in the configuration of rGO/Na2SO4/rGO. Device exhibited 165 F/g specific capacitance at scan rate 5 mV s−1 with cyclic retention of 94 % for 10,000 cyclic voltammetry cycles.

Dual storage mechanism of charge adsorption desorption and Faraday redox reaction enables aqueous symmetric supercapacitor with 1.4 V output voltage

Preparation of heterostructure electrode materials with dual storage mechanisms of charge adsorption desorption (electric double-layer capacitance) and Faraday redox reaction (pseudo-capacitance) remains a great challenge for supercapacitors with wide operating voltage and high energy density. Herein, the heterostructure ZnO nanoparticles decorated NiFe/CNTs/rGO (ZnO-FeNi/CG) was rational designed and synthesized via a straightforward two-step hydrothermal process for supercapacitor application. The rational designed flower-like heterostructure ZnO-FeNi/CG reveals outstanding specific capacitance of 1265F/g at 1 A/g and 88.5 % capacitance retention after 10,000 cycles even at 30 A/g in three-electrode test. Benefiting from the designed unique heterostructure and the effective anti-catalytic strategy, the Faradaic redox reactions of ZnO-FeNi/CG electrode were well coordinated by HER and OER, so that water splitting process was greatly suppressed under high operating voltage in aqueous alkaline electrolytes. Thus, the fabricated symmetric supercapacitor based on the dual storage mechanisms of electric double-layer capacitance and pseudo-capacitance displays 1.4 V output voltage, ultrahigh capacitance of 227F/g (1 A/g), and exceptional energy density of 62 Wh kg−1 at power density of 1400 W kg−1 as well as extraordinary capacitance retention 84.7 % for 10,000 cycles, outperforming the previous spinel-type metal oxides/carbon-based supercapacitors in aqueous alkaline electrolytes. The dual storage mechanism of charge adsorption desorption and Faraday redox reaction can provide a pathway to design next-generation aqueous symmetric supercapacitors with wide output voltage and ultrahigh energy density for advanced energy storage systems.

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.

Boosting the High Working Voltage of an Aqueous Symmetric Supercapacitor by a Phosphotungstic Acid-Based Coordination Polymer Coating with Polypyrrole

Boosting the High Working Voltage of an Aqueous Symmetric Supercapacitor by a Phosphotungstic Acid-Based Coordination Polymer Coating with Polypyrrole

Biomacromolecule-Assisted Synthesis and Electrocapacitive Behavior of Manganese Ferrite Nanoparticles

Two types of manganese ferrite nanoparticles, namely MF-SA and MF-CHI, have been synthesized solvothermally from the synthesis systems containing sodium alginate and chitosan, respectively. Both MF-SA and MF-CHI showed well crystalline nature based on the XRD and TEM measuremants. The larger saturation magnetization value of MF-SA should be ascribed to its slightly larger crystallite size than that of MF-CHI. Results from N adsorption-desorption isotherms and Raman spectra confirmed the structural difference in MF-SA and MF-CHI. The electrocapacitive behavior of manganese ferrite-based supercapacitors has been studied and MF-SA displayed a specific capacitance of around 60.4 F•g at 0.25 A•g in aqueous symmetric supercapacitors, larger than that of MF-CHI about 45.1 F•g at the same condition. MF-SA based supercapacitor also showed better capacitance maintenance of around 82% of the initial value at 1 A•g after 2000 cycle test than that of MF-CHI based cells. Based on the experimental data, the structure-property relationship of two types of MnFeO nanoparticles have been discussed and analyzed.

Erythritol-strengthen electrolytes effectively improve the electrochemical stability window of aqueous symmetric supercapacitor

Due to the advantages of high safety, high conductivity and low cost, the supercapacitor with aqueous electrolytes exhibits the great prospects in the future energy storage market. However, the narrow electrochemical stability window (ESW) of electric double-layer supercapacitor leads to its low energy density, which seriously limits its application. Herein, we demonstrate erythritol (Et) additive could efficaciously decrease the water molecules in the solvation sheath and break the hydrogen bond network of aqueous electrolytes, which resulting in expanded ESW. Especially, symmetric supercapacitor based on 37.9% Et additive to 1 M LiTFSI electrolyte expands ESW from 1.8 to 2.1 V, and the energy density increased to 13.3 Wh kg−1 with high specific capacitance of 86.6F g−1 and the capacitance retention rate of 73.8% after 10,000 cycles. Therefore, this study affords an efficient strategy to achieve high energy density aqueous supercapacitor.

A systematic study on Equisetum ramosissimum Desf. derived honeycomb porous carbon for supercapacitors: Insight into the preparation-structure-performance relationship

It is always of considerable significance for the development of high-performance carbon-based supercapacitors to regulate the porosity and understand the preparation-structure-performance relationship. In this work, a KOH-assisted hydrothermal pre-treatment combined with pyrolysis strategy is successfully employed to fabricate N-doped honeycomb-like three-dimensional porous carbon from Equisetum ramosissimum Desf. weeds. The pore structure is well-regulated by tuning the KOH concentration and carbonization temperature, thus optimizing the electrochemical properties. Three types of pore structures are proposed, and their differences and connections in terms of preparation and electrochemical performance are systematically explored. The carbon sample with the optimized pore structure delivers a high specific capacitance of 427 F g−1 at 0.2 A g−1 in the aqueous KOH electrolyte. When assembled into an aqueous symmetric supercapacitor device, the energy density reaches up to 30.9 Wh kg−1 at a power density of 500 W kg−1. The results indicate that a moderate Vmirco/Vmeso should play the key role in the excellent rate capability, while the co-contribution of double-layer capacitance and pseudo-capacitance as well as the rational pore size regulation should be responsible for the high specific capacitance.

Utilization of CO2 activated litchi seed biochar for the fabrication of supercapacitor electrodes

Biochar prepared from litchi seeds was investigated for the fabrication of supercapacitor electrodes. The specific capacitance of 190 F g−1 at 1 A g−1 current density was achieved in symmetric supercapacitor fabricated using biochar obtained at 700 °C. Upon activation using CO2, the capacitance was significantly enhanced, reaching up to 493 F g−1. Moreover, the charge-discharge cyclic stability of the activated biochar supercapacitor was well maintained with capacitance retention above 90% after 10,000 charge-discharge cycles in 1 M H2SO4 electrolyte. The energy and power density of the aqueous symmetric supercapacitor prepared using activated biochar were 24.6 Wh kg−1 and 0.6 kW kg−1, respectively. Physicochemical analysis of activated biochar using BET, XRD, Raman, TEM, and XPS revealed a high surface area, hierarchical porous structure, and heteroatom rich functionalities responsible for its excellent charge storage behaviour.