Aqueous Symmetric Supercapacitor Research Articles

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.

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.

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.

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.

Porous Carbon Nanofiber Flexible Membranes via a Bottlebrush Copolymer Template for Enhanced High-Performance Supercapacitors.

We report a method to construct ordered hierarchical porous structures in carbon nanofiber membranes using poly(ethylene oxide)-block-polydimethylsiloxane bottlebrush block copolymers (BBCPs) as templates. The BBCPs self-assemble into a spherical morphology driven by small-molecule hydrogen bond donors which act as bridges between carbon precursors and templates to promote uniform dispersion of the templates. We successfully obtained flexible, self-supporting, and porous carbon nanofiber membranes (PCNFs) with high porosity. Then, a supercapacitor electrode was independently prepared using PCNFs as an active substance without infiltrating any conductive agents or binders. The PCNFs exhibit excellent performance with a capacitance of 234.1 F g-1 at a current density of 1 A g-1 owing to the abundant hierarchical porous structures and high content of nitrogen and oxygen elements internally. The aqueous symmetric supercapacitor prepared using PCNFs electrodes maintains more than 95% capacitance retention after 55,000 charge-discharge cycles. Furthermore, the capacitance retention reaches up to 67.72% at a current density of 50 A g-1 (compared to 1 A g-1), exhibiting excellent cycling stability and rate capability. Based on the excellent electrochemical performance and flexible self-supporting ability of PCNFs, this work is expected to facilitate the development of flexible displays, flexible sensors, wearable devices, and electrocatalysis.

Effect of electrolyte and carbon material on the electrochemical performance of high-voltage aqueous symmetric supercapacitors

The energy storage capability of the aqueous supercapacitors is mainly attributed to the relatively low operating voltage of the device, as the thermodynamic decomposition voltage of water is 1.23 V. Therefore, the extension of the working voltage of the aqueous capacitor beyond the electrolyte decomposition limit is an important subject for the development of environmentally friendly energy storage devices. In this study, a commercial activated carbon (AC) and synthesized phosphorus-doped reduced graphene oxide (P-rGO) were used to gain insight into the influence of both textural properties and the surface chemistry on the electrochemical performance of high-voltage aqueous supercapacitors. Materials on the opposite end of the spectrum (highly porous, undoped AC and heteroatom-rich phosphorus-doped reduced graphene oxide with low porosity) were compared in a symmetric cell, operating in a wide voltage window of 2.0 V in 2 M NaClO4 electrolyte. Additionally, AC-based cell was tested in 1 M Na2SO4 solution to assess the differences in its performance in different sodium-based electrolytes. The obtained results demonstrate that both a porous structure and high contribution of heteroatoms, which improve the hydrophilicity of the electrode, are required to achieve high specific energy density values. However, with increasing current and higher power densities, a developed porous structure is required to maintain good energy storage characteristics. Achieving high operating voltage in the aqueous symmetric full-carbon supercapacitors is a promising energy storage solution. The assembled devices show a good specific energy density of up to 13 Wh kg−1 at a power density of 30 W kg−1.Graphical abstract

High-performance aqueous symmetric supercapacitors based on Ni6MnO8–MnCO3 composite self-supported electrodes

High-performance aqueous symmetric supercapacitors based on Ni6MnO8–MnCO3 composite self-supported electrodes can light up 72 LEDs for more than 2 minutes, which demonstrates an excellent practical application prospect.

N, S Codoping and Mesoporous‐Induced Capacitive Storage Enhancement in Supercapacitor and Improved Li–S Battery Performances of Polystyrene Waste‐Derived Carbon Electrode

The accumulation of solid polymer wastes stifles society's sustainable growth. Herein, N‐, S‐codoped polystyrene (thermocol) waste‐derived carbon is synthesized using a simple approach and utilized as an electrode for a lithium–sulfur battery and supercapacitor applications. The aqueous symmetric supercapacitor delivers a high specific energy of 60 and 27 Wh kg−1 at a specific power of 75 and 3780 W kg−1, respectively and 150 Wh kg−1 at a specific power of 520 W kg−1 in nonaqueous sodium‐ion capacitors with high cycling stability. Deconvolution by Dunn's and Trasatti's approaches reveals an enhanced capacitive‐charge storage rather than diffusive‐charge storage due to heteroatom doping and mesopores of the generated carbon. The lithium–sulfur battery delivers a stable capacity of 1079 mAh g−1 at 0.1C rate with excellent cycling stability over 500 cycles, suggesting improved mitigation of polysulfide dissolution imparted by the mesoporous carbon with thiophene moiety which effectively traps Li2S n .

Towards ultra-wide voltage window (3.2 V) aqueous symmetric supercapacitors triggered by hybridizing FeNiCo oxides with Ni(pyrithione)2 on FeNi foam

The low decomposition voltage (~1.23 V) of water enormously restricts the workable voltage of aqueous symmetrical supercapacitors (SSCs), which correspondingly limits the energy densities and frustrates the commercialization of aqueous SSCs. Herein, the voltage window of an all-solid-state symmetrical supercapacitors (ASSC) can be extended via employing a novel self-supporting hybrid electrode constructed by coupling FeNiCo oxides with Ni(pyrithione)2 on FeNi foam (denoted as NiPT@FeNiCo oxides/FNF) as both cathode and anode, which was synthesized using two-step hydrothermal processes. Primarily due to the introduction of redox-active pyrithione ligand chelating Ni ions supplemented by multiple pairs of reversible redox reactions to suppress water splitting, the assembled ASSC device exhibits an extra-wide workable voltage window up to 3.2 V with ultrahigh energy exporting densities (69.9 Wh kg−1 at 173.9 W kg−1, and 29.1 Wh kg−1 even at an elevated 2437.6 W kg−1). The energy density feature of this assembled ASSC device is superior to most existing transition metal oxide-based supercapacitors and even asymmetric or hybrid devices heretofore reported. After 10,000 cycles, this assembled ASSC device records a 92.5 % retention of initial area specific capacity. Our work offers a robust combination strategy to design high-potential electrode materials for constructing high-voltage ASSCs.

One-Pot In Situ Synthesis of Mn3O4/N-rGO Nanohybrids for the Fabrication of High Cell Voltage Aqueous Symmetric Supercapacitors: An Analysis of Redox Activity of Mn3O4toward Stabilizing the High Potential Window in Salt-in-Water and Water-in-Salt Electrolytes

The present work reports one-pot in situ synthesis of Mn3O4 nanocubes (average size = 33 nm) decorated on N-doped reduced graphene oxide to produce Mn3O4/N-rGO (N-GMn) nanohybrids by employing an aqueous reaction mixture of GO and greener reagent, glycine in the presence of MnCl2 under environmentally friendly mild conditions of temperature and near neutral pH ∼ 8. This process involves simultaneous reduction of GO and oxidation of Mn2+ species along with the doping of nitrogen forming Mn–O–C/O–Mn–N bonds to yield N-GMn nanohybrids, as confirmed by X-ray diffraction, Raman, Fourier transform infrared, and X-ray photoelectron spectroscopy studies. The N-GMn nanohybrids provide a high electrochemical potential window of −1.3 to +1.3 V, i.e., 2.6 V and −1.5 to +1.5 V, i.e., 3.0 V in neutral salt-in-water (0.5 M K2SO4) and water-in-salt (17 m NaClO4) electrolytes, respectively. Thus, the use of N-GMn as the electrode material, in which the integration of Mn3O4 and N-rGO takes place through covalent linkage (Mn–O–C/O–Mn–N), not only assisted in designing an aqueous symmetric supercapacitor in 17 m NaClO4 with high cell voltage (2.7 V) and energy density of 168 W h kg–1 at a power density of 675 W kg–1 but also contributed to achieve novel electrochemical attributes of a high cycling stability of 99.7% after 10,000 cycles. To the best of our knowledge, this is the first report on the Mn3O4/N-rGO-based symmetric supercapacitor, providing a high cell voltage of 2.7 V in an aqueous electrolyte comparable to the organic electrolyte-based commercial symmetric supercapacitor devices, thus demonstrating the importance of the present work for practical applications.

Internally-externally molecules-scissored ramie carbon for high performance electric double layer supercapacitors

Ramie carbon from the massively three-harvests-one-year and naturally channel-structured ramie straw is typically emerging as the excellent waste-biomass-utilization target toward high-performance electrochemical energy storage devices. However, the traditional activation strategies less fully optimize the pore distribution for the purpose of optimal energy storage capability. Herein, we reported the hierarchically interconnected three-dimensional ramie porous carbon based on waste ramie straw by internally-externally molecules-scissored activation strategy with pre-embedded KOH and re-added KOH molecules coordinately (in-ex-RPC). Benefiting from the synergistically internal-external activation strategy, this in-ex-RPC displays an excellent specific capacitance of 300 F g–1, which is much better than that of ramie porous carbon singly through pre-embedded KOH activation (in-RPC, 194 F g–1) or directly adding KOH activation (ex-RPC, 213 F g–1). Based on it, the aqueous symmetric supercapacitors display a cyclic capacity of 90.9%-retaining after 20,000 cycles at 5 A g–1. Therefore, this work may provide an effective strategy for energy storage applications of waste ramie straw and for further promoting waste biomass utilization.