High Capacitance Density Research Articles

Y-Shaped Acceptor-π-Donor-π-Acceptor Configured Anthraquinone-Tethered Phenothiazine Molecular Scaffold for High-Performance Organic Pseudocapacitors.

For the first time acceptor-π-donor-π-acceptor (A-π-D-π-A) based Y-type organic electrode material have been designed and successfully utilized in supercapacitor (SC) application. This Y-type molecular architecture coined as AQ-Im-PTZ-Im-AQ based on anthraquinone (AQ) (A)-imidazole (Im) (π)-phenothiazine (PTZ) (D)-imidazole (Im) (π)-anthraquinone (AQ) (A) in combination with graphite foil (GF). As-fabricated PTZ-Im-AQ/GF and AQ-Im-PTZ-Im-AQ/GF electrode have shown the good energy storage properties in three-electrode supercapacitor system. Moreover, two-electrode symmetric supercapacitor (SSC) device based on AQ-Im-PTZ-Im-AQ/GF electrode exhibited specific capacitance (Csp) of 68.97 F g-1 at 1 A g-1 current density. The specific electron density (ED) of SSC was observed to be 12.06 Wh kg-1 at a specific power density (PD) of 1798.50 W kg-1. The SSC device exhibited 81.62 % of Csp retention after 5000 galvanostatic charge-discharge (GCD) cycles. For real world applications, AQ-Im-PTZ-Im-AQ/GF electrode was tested in symmetric Csp coin cell with applied potential voltage window of -0.4 to 1.0 V was found to be 112.32 F g-1 at 0.5 A g-1. Moreover, it realized high specific capacitance and high energy density of 19.66 Wh kg-1 at 891.94 W kg-1 power density. As a results, AQ-Im-PTZ-Im-AQ/GF make as an attractive electrode material for application in next-generation SCs.

Giant enhancement and quick stabilization of capacitance in antiferroelectrics by phase transition engineering

The antiferroelectric-ferroelectric phase transition is a basic principle that holds promise for antiferroelectric ceramics in high capacitance density nonlinear capacitors. So far, the property optimization based on antiferroelectric-ferroelectric transition is solely undertaken by chemical composition tailoring. Alternately, here we propose a phase transition engineering tactic by applying pulsed electric stimulus near the critical electric field, which finally results in ~54.3% enhancement and quick stabilization of capacitance density in Pb0.97La0.02(Zr0.35Sn0.55Ti0.10)O3 antiferroelectric ceramics. Ex-situ and in-situ structural characterizations show that electric stimuli can induce the charming successive structural evolution, including domain evolution from multidomain to monodomain state, and modulation period change from 7.49 to 7.73. Structure-property correlation indicates that the antiferroelectric-ferroelectric phase transition engineering mainly stems from the unexpected irreversible recovery of the modulated structures. The present findings would deepen the understanding of the structural phase transition and provoke composition-independent post-treatment property innovation in the incommensurate antiferroelectric materials and devices.

3D Network Spacer-Embedded Flexible Iontronic Pressure Sensor Array with High Sensitivity over a Broad Sensing Range.

Microstructure construction is a common strategy for enhancing the sensitivity of flexible pressure sensors, but it typically requires complex manufacturing techniques. In this study, we develop a flexible iontronic pressure sensor (FIPS) by embedding an isolated three-dimensional network spacer (3DNS) between an ionic gel and a flexible Ti3C2Tx MXene electrode, thereby avoiding complex microstructure construction techniques. By leveraging substantial deformation of the 3DNS and the high capacitance density resulting from the electrical double layer effect, the sensor exhibits high sensitivity (87.4 kPa-1) over a broad high-pressure range (400-1000 kPa) while maintaining linearity (R2 = 0.998). Additionally, the FIPS demonstrates a rapid response time of 46 ms, a low limit of detection at 50 Pa, and excellent stability over 10 000 cycles under a high pressure of 600 kPa. As practical demonstrations, the FIPS can effectively monitor human motion such as elbow bending and assist a robotic gripper in accurately sensing gripping tasks. Moreover, a real-time, adaptive 7 × 7 sensing array system is built and can recognize both numeric and alphabetic characters. Our design philosophy can be extended for fabricating pressure sensors with high sensing performance without involving complex techniques, facilitating the applications of flexible sensors in human motion monitoring, robotic tactile sensing, and human-machine interaction.

A highly capacitive Graphene/Multiholed N‐CNTs hybrid evolved from black humate‐Co‐melamine precursor

Black humic acid (BA) is a black mixture of organic macromolecules isolated from humic acid, which has a greater potential for graphene transformation than fulvic acid and ulmic acid because of more and larger aromatic units and higher molecular weights exceeding 5000 Dalton. Here, chemically bonded BA‐Co‐Melamine precursors are initially constructed using different BA fractions as substrate, Co2+ as bridge bond and melamine as ligand. A series of Graphene/N‐CNTs hybrids (GNCs) is eventually synthesized after the precursor pyrolysis. Resultantly, Fraction Ⅰ, separated at a pH value of 4.16, plays a significant role on constructing the BA‐Co‐Melamine precursor and further producing multiholed GNCs. Due to abundant CNTs, rich mesopores, moderate nitrogen incorporation and a certain graphitized assembly structure, the prepared GNC‐Ⅰ‐b has high capacitance performances. The assembled AC//GNC‐Ⅰ‐b supercapacitor has high specific capacitance (147 F g‐1 at 0.5 A g‐1), rate capability, cycling stability and energy density (16.8 Wh kg‐1 at 14.4 KW kg‐1). The 2032 coin‐type Li//GNC‐Ⅰ‐b half‐cell has high initial discharge capacity (759 mAh g‐1 at 0.03 A g‐1), initial Coulombic efficiency (81.8%), rate performance and cycling stability. Hence, the GNC is a favorable high‐performance carbon material hopefully applied as electrode materials of supercapacitors and LIBs.

Highly Conductive Supramolecular Salt Gel Electrolyte for Flexible Supercapacitors.

Conductive gels have greatly facilitated the development of flexible energy storage devices, including supercapacitors, batteries, and triboelectric nanogenerators. However, it is challenging for gel electrolytes to tackle the trade-off issues between mechanical properties and conductivity. Herein, a strategy of all inorganic salt-driven supramolecular networks is presented to construct gel electrolytes with high conductivity and reliable mechanical performance for flexible supercapacitors. The salt gel is successfully fabricated by combining a salt supramolecular network constructed by NH4Mo7O24·4H2O and FeCl3·6H2O and a polymer network of poly(vinyl alcohol). The inorganic salt supramolecular network serves as a rigid self-supporting framework in the hydrogel system for improving the mechanical properties and providing abundant active sites for accelerating ion transport. Furthermore, the salt gel-enabled supercapacitors are equipped and exhibit a high specific capacitance (199.4 mF cm-2) and excellent energy density (27.69 μWh cm-2). Moreover, the flexible supercapacitors not only present remarkable cyclic stability after 3000 charging/discharging cycles but also exhibit good electrochemical stability even under severe deformation conditions. The strategy of salt-gel-driven flexible supercapacitors would provide fresh thinking for the development of advanced flexible energy storage fields.

High-Density Capacitive Energy Storage in Low-Dielectric-Constant Polymer PMMA/2D Mica Nanofillers Heterostructure Composite

The ubiquitous, rising demand for energy storage devices with ultra-high storage capacity and efficiency has drawn tremendous research interest in developing energy storage devices. Dielectric polymers are one of the most suitable materials used to fabricate electrostatic capacitive energy storage devices with thin-film geometry with high power density. In this work, we studied the dielectric properties, electric polarization, and energy density of PMMA/2D Mica nanocomposite capacitors where stratified 2D nanofillers are interfaced between the multiple layers of PMMA thin films using two heterostructure designs of the capacitors, PMMA/2D Mica/PMMA (PMP) and PMMA/2D Mica/PMMA/2D Mica/PMMA (PMPMP). The incorporation of a 2D Mica nanofiller in the low-dielectric-constant PMMA leads to an enhancement in the dielectric constant, with ∆ε ~ 15% and 53% for PMP and PMPMP heterostructures at room temperature. Additionally, a significant improvement in discharged energy density was measured for the PMPMP capacitor (Ud ~ 38 J/cm3 at 825 MV/m) compared to the pristine PMMA (Ud ~ 9.5 J/cm3 at 522 MV/m) and PMP capacitors (Ud ~ 19 J/cm3 at 740 MV/m). This excellent capacitive and energy storage performance of the PMMA/2D Mica heterostructure nanocomposite may inform the fabrication of thin-film, high-density energy storage capacitor devices for potential applications in various platforms.

Flexible zinc-ion hybrid supercapacitor based on Co2+-doped polyaniline/V2O5 electrode

With the rapid advancement of renewable energy sources and portable electronic devices, the demand for high-performance energy storage systems is growing, driving continuous progress in supercapacitor technology. Zinc-ion hybrid supercapacitors (ZIHS), known for their higher safety, cost-effectiveness, and environmental friendliness, have become a hot research topic. Vanadium pentoxide (V2O5) possesses flexible multivalence, low cost, low toxicity, wide voltage window, high capacitance, and high energy density. However, its poor electrical conductivity and low cycling stability hinder its electrochemical performance, thus limiting its application in ZIHS. Here, we propose a novel strategy of incorporating Co2+ ions and conductive polyaniline (PANI) with V2O5 (CoVO-PANI) as cathode materials for ZIHS. The synergistic effect between cobalt ions and polyaniline have led to an expansion of the interlayer spacing in CoVO-PANI, which reduce the binding energy of Zn2+ ion insertion, decrease the diffusion barrier of Zn2+ ion insertion, and enhanced the electronic conductivity of the material for electron transport. In result, the CoVO-PANI@CC//2 M ZnSO4//AC@CC can reach the areal capacitance of 847.3 mF cm−2 at 1 mA cm−2. Following 2000 times at 50 mA cm−2, the CoVO-PANI@CC//2 M ZnSO4//AC@CC maintains a retention rate of 81.37 %, and can achieve a Coulombic efficiency of 100 %. The assembled flexible ZIHS device exhibits excellent flexibility and stability, with an areal capacitance of 775.6 mF cm−2 at 1 mA cm−2. This work demonstrates the tremendous potential of CoVO-PANI@CC as a cathode material for ZIHS.

Energy storage chemistry: Atomic and electronic fundamental understanding insights for high-performance supercapacitors

The scarcity of fuels, high pollution levels, climate change, and other major environmental issues are critical challenges that modern societies are facing, mostly originating from fossil fuels-based economies. These challenges can be addressed by developing green, eco-friendly, inexpensive energy sources and energy storage devices. Electrochemical energy storage materials possess high capacitance and superior power density. To engineer highly efficient next-generation electrochemical energy storage devices, the mechanisms of electrochemical reactions and redox behavior must be probed in operational environments. They can be studied by investigating atomic and electronic structures using in situ x-ray absorption spectroscopy (XAS) analysis. Such a technique has attracted substantial research and development interest in the field of energy science for over a decade. The mechanisms of charge/discharge, carrier transport, and ion intercalation/deintercalation can be elucidated. Supercapacitors generally store energy by two specific mechanisms—pseudocapacitance and electrochemical double-layer capacitance. In situ XAS is a powerful tool for probing and understanding these mechanisms. In this Review, both soft and hard x rays are used for the in situ XAS analysis of various representative electrochemical energy storage systems. This Review also showcases some of the highly efficient energy and power density candidates. Furthermore, the importance of synchrotron-based x-ray spectroscopy characterization techniques is enlightened. The impact of the electronic structure, local atomic structure, and electronically active elements/sites of the typical electrochemical energy storage candidates in operational conditions is elucidated. Regarding electrochemical energy storage mechanisms in their respective working environments, the unknown valence states and reversible/irreversible nature of elements, local hybridization, delocalized d-electrons spin states, participation of coordination shells, disorder, and faradaic/non-faradaic behavior are thoroughly discussed. Finally, the future direction of in situ XAS analysis combined with spatial chemical mapping from operando scanning transmission x-ray microscopy and other emerging characterization techniques is presented and discussed.

Self-powered sensing platform for monitoring uric acid in sweat using cobalt nanocrystal-graphene quantum dot-Ti3C2TX monolithic film electrode with excellent supercapacitor and sensing behavior.

Thesynthesis of cobalt nanocrystal-graphene quantum dot-Ti3C2TX monolithic film electrode (Co-GQD-Ti3C2TX) is reportedvia self-assembly of Ti3C2TX nanosheets induced by protonated arginine-functionalized graphene quantum dot and subsequent reduction of cobalt (III). The resulting Co-GQD-Ti3C2TX shows good monolithic architecture, mechanical property, dispersibility and conductivity. The structure achieves excellent supercapacitor and sensing behavior. The self-charging supercapacitor produced by printing viscous Co-GQD-Ti3C2TX hydrogel on theback of flexible solar cell surfaceprovides high specific capacitance (296 F g-1 at 1 A g-1), high-rate capacity (153 F g-1 at 20 A g-1), capacity retention (98.1% over 10,000-cycle) and energy density (29.6 W h kg-1 at 299.9 W kg-1). The electrochemical chip produced by printing Co-GQD-Ti3C2TX hydrogel on paper exhibits sensitive electrochemical response towards uric acid. The increase of uric acid between 0.01 and 800μM causes a linear increase in differential pulse voltammetry signal with adetection limit of 0.0032μM. The self-powered sensing platform integrating self-charging supercapacitor, electrochemical chip and micro electrochemical workstation was contentedly applied to monitoring uric acid in sweats and shows one broad application prospect in wearable electronic health monitoring device.

(Digital Presentation) In-Situ Growth of CNT and Macroporous ZIF on Bacterial Cellulose for High Frequency Electrochemical Capacitor

High frequency electrochemical capacitors (HF-ECs) represent a class of devices characterized by their high capacitive density and operational capability within the hundreds or kilohertz range. As electronic devices continue to undergo downsizing trends, HF-ECs emerge as promising alternatives to bulky aluminum electrolytic capacitors (AECs), which are constrained by their limited working frequency of approximately 1 Hz and slow charge-discharge rates. The designing of electrodes of HF-ECs combines large surface area for capacitive density along with open porous network to facilitate rapid ion transport. In this study, we synthesized nickel coordinated ZIF-8 (Zeolitic Imidazole Framework-8) cages on bacterial cellulose (BC). The samples underwent rapid carbonization in the presence of dicyandiamide at ~950˚C for 20 minutes, during which the zinc centers inside the MOF cages evaporated forming macroporous structures, while the nickel particles gave rise to carbon nanotube (CNT) growth through tip growth mechanism. The uniform coverage of BC with macroporous ZIF cages reduces the microporous effect, while the CNT growth also imparts higher electronic conductivity via graphitic nitrogen groups. The HF-ECs made with these electrodes and 6M KOH aqueous electrolyte gave a capacitive density of ~3.4 mFcm-2 and a phase angle of -81.3˚. The electrodes were stacked in pairs of 2 and 3 to achieve higher capacitance of 6.3 mFcm-2 and 8.9 mFcm-2 respectively. The HF-ECs were also assembled with 1 M TEABF4 in acetonitrile to show higher working voltage of these electrodes. The device maintained a capacitance just above 3 mFcm-2 and a phase angle over -80˚. The cells show an excellent working capability at higher discharge rates of 100 mAcm-2, where they retained ~70% of the initial capacitance. Figure 1

Supercapacitors on hairs with quantum capacitance-dominant extraordinary capacitance

Graphene-based planar microsupercapacitors are promising energy storage devices for microelectromechanical systems. However, the capacitance and energy density of such graphene-based microsupercapacitors cannot achieve further promotion because of the lack of strategies that permit tailoring both chemical and geometric structures of graphene at the nanoscale. In this study, supercapacitors on hairs with quantum capacitance-dominant extraordinary capacitance are found. Simulations reveal that the record high capacitance and energy density are attributed to the enhanced quantum capacitance effect. The graphene electrodes are prepared by femtosecond laser direct writing-assisted reduction and N-doping of graphene oxides on the human hair surface. Due to the distinct quantum capacitance dominance, the microsupercapacitors exhibit extremely high capacitance (∼3000 mF/cm2) and energy density (∼417 μWh/cm2). We hope that this work will promote the development of microsupercapacitors with high capacitance and energy density.

Synthesis of tin oxide nanoparticles by chemical and biological methods and their applications in high performance supercapacitor electrode, antibacterial and antifungal activity

The advancement of supercapacitor technology is impeded by a dearth of advanced electrode materials that can augment energy storage capabilities. In this-work, we propose a novel, sustainable methodology for synthesizing tin oxide nanoparticles (SnO2-PJ NPs) utilizing Prosopis juliflora aqueous leaf extract as a stabilizing and reducing agent for the first time. These nanoparticles were evaluated in comparison to those synthesized via traditional chemical methods (SnO2-pure NPs). The samples were analyzed using an array of techniques including UV, FTIR, EDX, SEM, PL, XRD and XPS. The results indicated that the SnO2-PJ NPs exhibited superior performance as supercapacitor electrodes in both three-electrode and two-electrode system configurations. The symmetric supercapacitor device SnO2-PJ NPs displayed a high specific capacitance (98 F g−1 at 1 A g−1) and energy density (31 Wh kg−1 at 0.35 kW kg−1) in an acidic electrolyte of 1 M H2SO4. Additionally, the SnO2-PJ NPs demonstrated exceptional cycling stability, maintaining 100% of their specific capacitance after 10,000 cycles. In conclusion, the SnO2-PJ NPs exhibit tremendous potential as a next-generation energy storage material, owing to their high-power density, high-energy density, and outstanding capacity. Additionally, antibacterial and antifungal activity of synthesized SnO2 NPs is studied. The bio-synthesized SnO2 PJ NPs possesses highest antibacterial activity against two Gram-positive bacteria Staphylococcus aureus (17.0 ± 0.08 mm) and Bacillus subtilis (17.5 ± 0.74 mm) as well as one Gram-negative bacteria Escherichia coli (15.0 ± 0.06 mm) at 200 μl. Furthermore, the bio-synthesized SnO2 PJ NPs possesses highest antifungal activity against Aspergillus niger (10.0 ± 0.11 mm) and Aspergillus flavus (08.0 ± 0.12 mm) at 200 μl. The present work demonstrated an eco-friendly preparation of SnO2 NPs with high-performance supercapacitor electrode, good antibacterial and antifungal properties.

High-Performance TiO2/ZrO2/TiO2 Thin Film Capacitor by Plasma-Assisted Atomic Layer Annealing.

Although laminate structures are widely used in electrostatic capacitors, unavoidable heterogeneous interfaces often deteriorate the dielectric properties by impeding film crystallization. In this study, a TiO2/ZrO2/TiO2 (TZT) laminate structure, where upper-TiO2 deposited on the heterogeneous interface was crystallized by plasma-assisted atomic layer annealing (ALA), was investigated. ALA effectively induced the phase transition of the upper-TiO2 from the amorphous or anatase phase to the rutile phase, leading to an increase in the dielectric constant, whereas the ZrO2 blocking interlayer maintained the amorphous phase owing to the extremely localized effect of ALA. Consequently, through the layer-by-layer phase control of ALA, the dielectric constant of the upper-TiO2 was enhanced by 25% by applying ALA, leading to an increase in a capacitance density of 27% of the TZT capacitor, whereas a low leakage current density of ∼10-8 A/cm2 was maintained (at 1 V). In addition, the TZT capacitor on three-dimensional structures (aspect ratio of 5:1) shows a high capacitance density of up to 461 nF/mm2 owing to ALA.

Multi-layers hexagonal hole MXene trap constructed by carbon vacancy defect regulation strategy enables high energy density potassium-ions storage

Due to the slow reaction kinetics of potassium-ions with large size radius in layered materials, the energy density of aqueous potassium-ion hybrid supercapacitors (PIHCs) is severely limited. At the same time, the treatment of defects is a “double-edged sword” in energy storage materials, which requires targeted and precise regulation. In order to solve this problem, multi-layers hexagonal hole MXene trap was constructed by using the carbon vacancy defect regulation strategy, and high specific capacitance and energy density potassium-ion storage was realised in PIHCs. The structure-activity relationship at the atomic level was elucidated in combination with the pseudo-capacitance effect caused by the change of valency of newly exposed titanium atoms in the inner wall of the hexagonal hole MXene trap. By density functional theory, the adsorption energy and kinetic analysis of multi-layers hexagonal hole MXene for potassium-ions were calculated, and the optimal position and quantity of potassium-ions were determined. By quantitative analysis of electron band structure and differential charge density, the internal mechanism of high conductivity and energy density of multi-layers hexagonal hole MXene PIHCs was revealed.

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.

High energy-storage density and giant negative electrocaloric effect in PLZS antiferroelectric thick film ceramics prepared via the tape-casting process

Antiferroelectric materials are highly desired for high energy-storage density capacitors and electrocaloric refrigerator in the future due to their excellent energy storage properties and giant negative electrocaloric effect, which have attracted great attention in recent years. In the present work, a highly recoverable energy density (Wrec) and a large reversible adiabatic temperature change (ΔT) were obtained simultaneously in PLZS thick film ceramics (TFCs). A maximum Wrec of 9.84 J·cm−3 with an efficiency of 85.2 % at 440 kV·cm−1, and a negative ΔT of −9.50 °C at 280 kV·cm−1 were obtained. Moreover, the maximum value of electrocaloric strength of 0.98 K·m·MV−1 was achieved for Pb0.97La0.02(Zr0.50Sn0.50)O3 TFCs. These results demonstrate that the PLZS TFCs can be applied potentially for high energy-storage density capacitors and refrigerators.

WITHDRAWN: Multi-layers hexagonal hole MXene trap constructed by carbon vacancy defect regulation strategy enables high energy density potassium-ions storage

Due to the slow reaction kinetics of potassium-ions with large size radius in layered materials, the energy density of aqueous potassium-ion hybrid supercapacitors (PIHCs) is severely limited. At the same time, the treatment of defects is a "double-edged sword" in energy storage materials, which requires targeted and precise regulation. In order to solve this problem, multi-layers hexagonal hole MXene trap was constructed by using the carbon vacancy defect regulation strategy, and high specific capacitance and energy density potassium-ion storage was realized in PIHCs. The structure-activity relationship at the atomic level was elucidated in combination with the pseudo-capacitance effect caused by the change of valency of newly exposed titanium atoms in the inner wall of the hexagonal hole MXene trap. By density functional theory, the adsorption energy and kinetic analysis of multi-layers hexagonal hole MXene for potassium-ions were calculated, and the optimal position and quantity of potassium-ions were determined. By quantitative analysis of electron band structure and differential charge density, the internal mechanism of high conductivity and energy density of multi-layers hexagonal hole MXene PIHCs was revealed.

Combined Ce-doping and electrochemical activation strategies for boosting the supercapacitance of NiCoO

Heteroatom doping and electrochemical activation have been reported to improve electrochemical performance of electrode materials. However, there is no report about the combination of these two methods to enhance the electrochemical performance of NiCo-oxides. Herein, Ce-doped NiCoO nanocones are grown on porous nickel foam, and electrochemical activation tactic is utilized to further boost the electrochemical performance. Through adjusting the Ce-doping dosage, the optimized NiCoCe-0.25 sample presents the highest capacitance of 1800 F g−1, greatly higher than that of pristine NiCoO (969.4 F g−1). The optimized NiCoCe-0.25 is selected as initial electrode for seeking the best activation condition. The activation process in KOH electrolyte triggers the formation of nanosheets on the surface of nanocones, followed by the growing of thin nanosheets. Therefore, the activation mechanism of Ce-doped NiCoO involves the generation and growing of nanosheets, accompanied by the composition transition from oxides to hydroxides/oxyhydroxides. When lasted for 430 CV cycles, the activation product delivers the maximum capacitance of 3795.8 F g−1 (1897.9 C g−1) at 1 A g−1. The superior performance is attributed to the interconnected framework structure consisted of nanosheets and nanoparticles, as well as the optimized composition. When utilized as positive electrode in a supercapacitor device, Ce-doped NiCoO electrode exhibits a high specific capacitance, cycling stability, and energy density. Therefore, Ce-doping and electrochemical activation tactic can be integrated for enhancing the supercapacitance performance of metal oxides.

The production of electrodes for microsupercapacitors based on MoS2-modified reduced graphene aerogels by 3D printing

Micro-supercapacitors (MSCs) are of interest because of their high power density and excellent cycling performance, offering a broad array of potential applications. However, preparing electrodes for the MSCs with an extremely high areal capacitance and energy density remains a challenge. We constructed MSC electrodes with an ultra-high area capacitance and a high energy density, using reduced graphene oxide aerogel (GA) and MoS2 as the active materials, combined with 3D printing and surface modification. Using 3D printing, we obtained electrodes with a stable macrostructure and a GA-crosslinked micropore structure. We also used a solution method to load the surface of the printed electrode with molybdenum disulfide nanosheets, further improving the electrochemical performance. The surface capacitance of the electrode reached 3.99 F cm−2, the power density was 194 W cm−2, and the energy density was 1 997 mWh cm−2, confirming its excellent electrochemical performance and cycling stability. This work provides a simple and efficient method for preparing MSC electrodes with a high areal capacitance and energy density, making them ideal for portable electronic devices.

Enriched performance of practical device assisted asymmetric supercapacitor: NiO/Co3O4 intercalated with rGO nanocomposite electrodes

In this present report, we developed high performance supercapacitor electrode material of NiO/Co3O4/rGO ternary nanocomposites synthesized by a hydrothermal method with a different nickel and cobalt molar proportions. The phase formation, surface morphology and elemental information studies of binary NiO/Co3O4 and ternary NiO/Co3O4/rGO nanocomposites were investigated. The electrochemical investigations of the binary and ternary nanocomposites electrodes have been examined. Compare with various molar proportions, the ternary NiO/Co3O4(1,3)/rGO nanocomposites shows an extraordinary capacitance value of 980 Fg−1 at 1 Ag−1 as well as robust cycle life (cyclic retention of 92 % over the 5000 cycles at 10 Ag−1). In 0–1.4 V, an asymmetric supercapacitor attained a specific capacitance of 87.2 Fg−1 and large power density (1396.3 W/kg) with extreme energy density (23.7 Wh/kg). Moreover, assembled device reveals a great rate capability (89 % over the 5000 cycles in the electrolyte of PVA-KOH). The ternary electrode has high capacitance, capacitance retention and large energy density due to NiO and Co3O4 nanoparticles being intercalated with the high surface of rGO, as well as the synergetic effect of NiO/Co3O4 and rGO.