Assembled Asymmetric Supercapacitor Research Articles

NiAl LDH nanosheets based on Ag nanoparticles-decoration and alkali etching strategies for high performance supercapacitors

Layered double hydroxides (LDHs) represent a category of two-dimensional layered intercalation materials, showing significant potential as electrode materials for the production of high-energy-density supercapacitors due to their tunable composition, ease of synthetic modification, and low cost. Here, we constructed alkali-etched NiAl LDH-OH nanosheets/Ag nanoparticles (NPs) composite material (Ag@NiAl LDH-OH) for high-performance supercapacitors through a simple solvent-thermal reaction. The alkali treatment is employed to selectively etch some Al3+ ions, generating cation vacancies as active sites for energy storage. Additionally, under the simultaneous influence of strong alkalis and vacancies, the interlayer spacing of LDHs expands, aiding in the promotion of interlayer ion mobility. Meanwhile, the decoration of silver nanoparticles ensures excellent electron conductivity in the NiAl-LDH-OH nanosheets, thereby facilitating improved utilization of the active substance and achieving outstanding rate performance. The Ag@NiAl LDH-OH electrode, when prepared, demonstrates a significant increase in specific capacitance, reaching 1790 F g-1 at a current density of 1 A g-1. This represents approximately 7 times the specific capacitance of the pristine NiAl LDH electrode, with a capacity retention of 79% even under a high current density of 20 A g-1. Moreover, the assembled asymmetric supercapacitor (ASC) attains a maximum energy density of 138.25 Wh kg-1 at a power density of 700 W kg-1, maintaining 81% of its initial specific capacitance after 20000 cycles. This research introduces novel pathways for advancing high-energy-density SCs.

Exploring the effect of morphology on electrochemical performance of nickel and cobalt metal-organic frameworks and their derivatives for supercapacitor and hydrogen evolution

This study explores the novel approach of investigating the use of binder-free nickel and cobalt metal-organic frameworks and their metal oxide derivatives in 1D, 2D, and 3D morphologies on Ni foam for applications in supercapacitors and hydrogen evolution. This research work involves changing parameters like precursor concentration, organic linkers, and reaction time, leading to the formation of stable one-, two-, and three-dimensional NiO and Co3O4 nanostructures. The morphologies of pristine MOFs and their corresponding oxides were comprehensively verified through FESEM analysis. Significantly, the materials with two-dimensional growth exhibited superior electrochemical performance in supercapacitors and good electrocatalytic performance in hydrogen evolution reaction when compared to their one-dimensional and three-dimensional counterparts. Among them, 2D NiO demonstrated exceptional performance as a supercapacitor electrode, with a specific capacity of 688.13 C g−1 (1376.26 F g−1) at 1 A g−1, surpassing 1D and 3D NiO nanostructures. It also demonstrated good stability by retaining 93.1 % of its initial capacity after 5000 cycles at 10 A g−1. The assembled asymmetric supercapacitor (ASC) achieved a high energy density of 65.27 Wh kg−1 at 375 W kg−1, maintaining 33.18 Wh kg−1 even at 7500 W kg−1. It also maintained 87.8 % retention of its initial capacity up to 5000 cycles at 10 A g−1. Furthermore, when tested for HER, all oxides exhibited better performances with specifically 2D NiO exhibiting good catalytic performance, reaching 10 mA cm−2 at a low overpotential of 129 mV (vs. RHE) and displaying remarkable stability over 24 h. This study upholds the superiority of two-dimensional sheet-like structures with interconnected network of nanoparticles in electrochemical and electrocatalytic performance compared to one-dimensional rod-like and three-dimensional pyramid-like structures.

Mixed metal oxide-based binder-free electrode and redox additive electrolyte combination for enhanced supercapacitor performance

In this study, a novel Co3O4/CeO2 nanocomposite for supercapacitors was fabricated through a one-step hydrothermal method, to achieve distinct crystalline phases and a unique flower-like structure. Integrated into a binder-free electrode (BFE) on Ni foam, the Co3O4/CeO2@NF electrode outperformed individual Co3O4 and CeO2-based electrodes. The synergistic effect between Co3O4 and CeO2, enhances the overall surface area, porosity and conductivity of the composites, which improved the supercapacitor characteristics. Detailed analyses confirmed the Co3O4/CeO2@NF electrode's superior cyclic voltammetry, galvanostatic charge-discharge, rate capability, and stability under potassium hydroxide (KOH) and redox additive electrolytes (RAE). The incorporation of RAE further boosted the performance, showcasing the potential for advanced energy storage applications. The assembled asymmetric supercapacitor (ASC) device exhibited outstanding energy and power densities, making it promising for practical applications. Comprehensive electrochemical impedance spectroscopy (EIS) studies offered insights into charge transfer dynamics, highlighted the positive impact of redox additives. This work contributed to understand the synergistic effects in metal oxide composites on advancing the high-performance supercapacitor development.

Facile one-step hydrothermal synthesis of zinc vanadate nanomaterials enhanced via reduced graphene oxide for ultra-long life asymmetric supercapacitors

The novel transition metal vanadate materials with hierarchical nanostructures have attracted considerable attention due to their remarkable electrochemical properties in catalysis and energy storage/conversion systems. Herein, we report the zinc vanadate (Zn3V2O10) nanomaterials (ZVO NMs) by a simple one-step hydrothermal method. The synthesis of ZVO NMs is studied at different growth temperatures (100, 150, and 200 °C). Additionally, reduced graphene oxide (rGO) sheets are introduced into the optimized ZVO NM obtained at 150 °C (i.e., ZVO NM-150). The prepared materials are analyzed by various characterization techniques and the obtained properties of ZVO NM with rGO sheets are beneficial for energy storage devices. The ZVO NM-150@rGO electrode exhibits a high specific capacity (capacitance) of 95 mAh g−1 (677 F g−1) at 2 A g−1 with a rate capability of 82 % in 1 M KOH aqueous electrolyte solution. The ZVO NM-150@rGO electrode reveals superior capacity retention of 105 % with Coulombic efficiency (CE) of 98 % after completing 45,000 cycles. Furthermore, the assembled asymmetric supercapacitor (ASC) device demonstrated maximum energy and power densities of 19.06 Wh kg−1 and 2190.78 W kg−1, respectively. The ASC device also shows good cycling stability with excellent capacitance retention of 139 % and CE of 98 % after 80,000 cycles. Benefiting from these advantageous properties, the ZVO NM and ZVO NM-150@rGO electrode materials are very promising for high-performance SCs.

Carboxymethylcellulose/poly(3,4-ethylenedioxythiophene):polystyrene sulfonate membrane after dimethyl sulfoxide treatment for flexible and high electrochemical performance asymmetric supercapacitors

As the requirements for wearable electronic devices continue to increase, the development of bendable and foldable supercapacitors is becoming critical. However, it is still challenging to design free-standing electrodes with flexibility and high electrical conductivity. Herein, using carboxymethylcellulose (CMC) as the biological template and poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) as the electroactive material, a flexible CMC/PEDOT:PSS membrane with a cross-linked mesh structure was firstly synthesized by a facile in-situ polymerization and vacuum filtration process. Subsequently, the CMC/PEDOT:PSS membrane was further treated with dimethyl sulfoxide (DMSO) to remove the excess PSS, thereby enhancing their electrochemical performance. The results showed that the best performing hybrid membrane had good mechanical properties (tensile strength of 48.1 MPa) and high electrical conductivity (45.1 S cm−1). The assembled asymmetric supercapacitor (ASC) is capable of delivering an energy density of 181.9 μW h cm−2 at a power density of 750 μW cm−2 and maintains an initial capacitance of 93.4 % and a coulombic efficiency of 100 % after 10,000 GCD cycles, demonstrating an ultra-long cycle life. Moreover, good electrochemical properties can be retained even in the bent and folded state. Therefore, the hybrid membrane electrode with both flexibility and high electrochemical performance has great potential for application in wearable electronics.

Electrosynthesis of Co[sbnd]Mn layered-double-hydroxide as a precursor for Co-Mn-MOFs and subsequent electrochemical sulfurization for supercapacitor application

Today, researchers are focusing on improving the electrochemical efficiency of supercapacitors by designing and evolving synthesis routes for battery-type hierarchical materials. This study proposes a green method for creating high-efficiency positive electrode materials with a mesoporous heterostructure on Ni foam (NF) using a metal-organic framework (MOF)-derived approach. A binder-free electrosynthesis technique was utilized to grow CoMn-layered double hydroxide (CoMn-LDH) and exchange ions to obtain a porous metal precursor, namely binary Co-Mn-MOF. The MOF arrays were then electrochemically converted to CoMn-sulfide (CMS), which exhibits excellent conductivity and a mesoporous structure, enabling it to serve as a 3D continuous network for ion and electron conduction in energy storage. The synthesized sample was characterized using various techniques, including field-emission scanning electron microscopy (FESEM), elemental mapping, high-resolution transmission electron microscopy (HR-TEM), energy-dispersive X-ray analysis (EDX), Brunauer-Emmett-Teller (BET) surface area analysis, X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD). Among the prepared electrode samples, CoMn−S with an Mn/Co feeding ratio of 1:2 demonstrated outstanding electrochemical properties. Based on this platform, CMS was applied and validated as a positive electrode in supercapacitors, exhibiting a high specific capacity of 1091C g−1 at 1 A g−1 in a three-electrode configuration and remarkable cycling life (85 % capacitance retention over 7000 cycles at 25 A g−1). Furthermore, an assembled asymmetric supercapacitor (ASC) device using CMS as the cathode and AC as the anode demonstrated satisfactory electrochemical performance. The CMS//AC device delivers an energy density of 84 Wh kg−1 at a high power density of 1191.4 W kg−1 and maintains stable electrochemical stabilities (92 % capacitance retention even after 7000 cycles). This synthesis approach opens up a new avenue for developing binder-free electrodes with hierarchical structures using metal sulfides, thereby enhancing the electrochemical performance of hybrid supercapacitors.

Rational design of nickel‑cobalt sulfide nanorods grown on graphene with high performance for supercapacitors

Nickel cobalt sulfides have exhibited great promise as supercapacitor electrode materials owing to the abundant redox states and considerable theoretical capacities. However, they still suffer from sluggish reaction kinetics, resulting in undesirable capacitance, cyclic and rate performances. Herein, electrochemical exfoliated graphene with high dispensability was utilized as the matrix and uniform nickel‑cobalt sulfide nanorods grown on graphene (Ni-Co-S/G) was achieved by a facile two-step strategy for enhanced capacitive performances. This well-constructed Ni-Co-S/G can provide plentiful active sites for electrochemical reaction, offer more efficient and rapid electron/ion transfer pathways during the charge/discharge process, and the tight contact of nickel‑cobalt sulfide nanorods and graphene can improve the stability. Consequently, the obtained Ni-Co-S/G electrode exhibits a high specific capacity of 1579.68 F g−1 at 1 A g−1, splendid rate capability (1240 F g−1 at 20 A g−1) and excellent cycling stability with capacity retention of 91.5 % after 5000 cycles at 5 A g−1. Additionally, the assembled asymmetric supercapacitor (ASC) device Ni-Co-S/G//AC with Ni-Co-S/G and commercial active carbon as positive and negative electrode displays an energy density of 75.3 W h kg−1 at the power density of 1125 W kg−1, still retaining 50.5 Wh kg−1 even at 16.9 kW kg−1. This work provides a potential strategy to design high-performance nickel‑cobalt sulfides electrode for advanced supercapacitors.

CoNi hydroxides functionalized by borate ions with loose porous structure for the boosting of supercapacitor performance

Developing low-cost and highly efficient electrode is essential for energy storage and conversion device. Herein, CoNi hydroxide nanosheets functionalized by borate ions (denoted as CoNiB) are fabricated via a convenient wet chemical process and subsequent hydrothermal boronization reaction. It is observed that rapid generation of hydrogen in the boronization process favors the formation of nanosheets. Moreover, hydrogen as a gas template is conductive to the formation of 3D loose porous structure which not only facilitates electrolyte penetration, but also exposes more active sites and accelerates the transport of ions and electrons. Resulting from the unique hierarchical microstructure, the optimized CoNi(1:1)B electrode delivers a high specific capacity of 283.25 mAh/g at 1 A g−1 as well as good rate capability (259.38 mAh/g at 20 A g−1) and stability. Besides, the assembled asymmetric supercapacitor (ASC) device with CoNi(1:1)B as positive electrode and activated carbon as negative electrode displays an outstanding energy density of 64.7 Wh kg−1 at 814.7 W·kg−1 with good cyclability (93 % after 15,000 cycles), verifying the great application potential of CoNi(1:1)B in practice.

Nanoflower-like Cu2CoSnS4 grown on nickel foam as binder-free electrode material for asymmetric supercapacitors with high rate and capacitance

The self-supporting binder-free electrode material with a special porous structure and abundant electrochemical active sites is viewed as the ideal electrode material for supercapacitors. In this work, nanoflower-like Cu2CoSnS4 was first constructed on nickel foam (NF) substrate (CCTS/NF) by a one-step solvothermal method. The nanoflower-like shape increases the channels for ion transport and presents a massive quantity of active sites, which is crucial to improving electrochemical performance. What’s more, the significant synergistic effect between the ternary transition metal ions enhances the electrochemical performance as well. As a result, the CCTS/NF-3 performs a standout specific capacitance of 1690 mF cm-2 at 2 mA cm-2, a perfect rate performance of 79.6% and a superb cycle consistency of 99.6% after 5000 cycles. The assembled asymmetric supercapacitor (ASC) performs a high potential window of 0–1.4 V, a superb energy density of 0.0065 mWh cm-2 at 0.14 mW cm-2 and magnificent capacitance remains (95.6% after 5000 cycles). The electrode material has low acquisition cost and terrific electrochemical performance, and has broad utility possibilities in the supercapacitor market.

High-performance asymmetric supercapacitor based on nickel-MOF anchored MXene//NPC/rGO

MXene has been considered a viable 2D electrode material for supercapacitors due to its good conductivity and remarkable cycling stability. However, its low specific capacitance has limited its applications. To address this, we deposited nickel-metal–organic-framework (Ni-ZIF-67) on MXene. Firstly, Ni-ZIF-67 composites were synthesized at various temperatures (150–450 ℃), with different masses of Ni. Among the Ni-ZIF-67 (NZ) composites, the NZ-R-2-200 electrode exhibited the largest specific surface area of 549.78 m2/g, and the highest specific capacity of 365.5 C/g at 0.5 A/g. Then, the NZ-R-2-200/K-Ar-MXene composite was prepared by decorating intercalated 2D MXene (K-Ar-MXene) with NZ-R-2-200. NZ-R-2-200 were anchored on the surface of K-Ar-MXene. Significantly, an electrode based on NZ-R-2-200/K-Ar-MXene composite demonstrates a remarkable specific capacity of 557 C/g at 0.5 A/g and long-time stability of 66 % capacitance retention after 5000 cycles at 2 A/g. An assembled asymmetric supercapacitor (ASC) based on NZ-R-2-200/K-Ar-MXene as the positive and porous carbon composite of (NPC/rGO) as the negative electrodes showed a high energy density of 27.48 Wh/Kg and a power density of 400 W/Kg combined with cyclic stability up to 2000 cycles.

Designed formation of C/Fe3O4@Ni(OH)2 cathode with enhanced pseudocapacitance for asymmetric supercapacitors

The rational design and synthesis of advanced electrode materials are significant for the applications of supercapacitors. Ferroferric oxide (Fe3O4), with its high theoretical capacitance is a renowned cathode material. Nevertheless, its low electronic conductivity and poor cycling stability during a long-term charge/discharge process limit its large-scale applications. In this work, the precise modulation of multiple components was reported to enhance electrochemical performance. The ternary heterostructures were fabricated by wrapping ultrathin nickel hydroxide (Ni(OH)2) nanosheets on the surfaces of Fe3O4 nanoparticles-loaded on sodium carboxymethyl cellulose (CMC)-derived porous carbon, named as C/Fe3O4@Ni(OH)2. Due to the large specific surface area and excellent conductivity of CMC-derived porous carbon and the abundant reaction sites of Ni(OH)2 nanosheets, the optimized C/Fe3O4@Ni(OH)2–1.0 sample exhibited the highest specific capacitance of 3072F g−1 at a current density of 0.5 A g−1. Furthermore, the assembled asymmetric supercapacitor (ASC) with activated carbon and C/Fe3O4@Ni(OH)2–1.0 as the negative and positive electrodes, respectively, showed an energy density of 123 W h kg−1 at 381 W kg−1, and a long-life stability with an excellent capacitance retention of 90.04 % after 10,000 cycles. The route for preparing composite electrode materials proposed in this work provides a reference for realizing high-performance energy storage devices.

Rapid Amorphization in MOF/Metal Selenite Nanocomposites for Enhanced Capacity in Supercapacitors.

MOF/inorganic nanocomposites combine the advantages of each component. Herein, two MOF/metal selenite nanocomposites, Co-NH2-BDC/CoSeO3·H2O and Co-BDC/CoSeO3·H2O, are prepared on nickel foam through a facile two-step hydrothermal method, which inherit the 2D morphology and porosity properties of their MOF precursors. Furthermore, during the electrochemical activation process, the crystallized nanocomposites can easily transform into amorphous structures in a short time of 20 min in the presence of an electric field, similar to CoSeO3·H2O. Due to amorphization, the electrochemical performance of the two nanocomposites is much enhanced relative to that of their MOF precursors. Specifically, the areal capacitances of Co-NH2-BDC/CoSeO3·H2O and Co-BDC/CoSeO3·H2O are 5.35 and 10.65 F·cm-2 at 2 mA·cm-2, respectively. The assembled asymmetric supercapacitor (ASC) using Co-NH2-BDC/CoSeO3·H2O as positive electrodes delivers an energy density of 0.207 mWh·cm-2 at a power density of 0.799 mW·cm-2 with outstanding cycling stability (93% capacity retention after 5000 cycles). Using Co-BDC/CoSeO3·H2O as positive electrodes, the ASC can reach a high energy density of 0.483 mWh·cm-2 at a power density of 0.741 mW·cm-2 and 84% capacity retention after 5000 cycles. This work provides an efficient strategy for constructing MOF/metal selenite nanocomposites for energy storage and conversion.

Amorphous S-doped NixCo3-xO4 for high-performance asymmetric supercapacitors

Amorphous S-doped NixCo3-xO4 materials were successfully synthesized using a facile co-precipitation method through changing additive in a mixed solution. As-prepared amorphous S-doped NixCo3-xO4 exhibit different Ni/Co ratio, O/S ratio, morphology and structure when a mixed solution including sodium dodecyl sulfate, without additive, or containing glycine. S-doped NixCo3-xO4 prepared with a mixed solution excluding additive (denoted as NixCo3-xO4-ySy-2) exhibits remarkable supercapacitive performance due to optimum Ni/Co ratio, minimum O/S ratio, proper morphology and structure. NixCo3-xO4-ySy-2 delivers a specific capacitance of 1335 F g−1 at 0.5 A g−1 and a ultra-high specific capacitance retention of 68.7% even at 16 A g−1, demonstrating high specific capacitance and good rate capability. Moreover, NixCo3-xO4-ySy-2 shows an initial specific capacitance retention of 80.8% after 2000 cycles, implying superior cycling stability. The assembled asymmetric supercapacitor (ASC) based on NixCo3-xO4-ySy-2 as the positive electrode and AC as the negative electrode achieves outstanding energy density of 31.87 Wh kg−1 at a power density of 900 W kg−1. The specific capacitance retention of the ASC is up to 90.2% after 2000 cycles, exhibiting excellent cycling stability. This study shows a promising electrode for supercapacitors device and provides an effective strategy for design of high-performance supercapacitor electrode materials.

Facile synthesis of helical Co-based coordination supramolecular network micro-nano rods as a durable cathode for high-performance asymmetric supercapacitors and aqueous Co-Zn batteries

Developing and exploring new-type electrode materials with powerful components and suitable morphologies for well-pleasing energy storage and conversion is an important task. Herein, a novel cobalt-based coordination supramolecular network (Co-CSN) material with a helical rod-like morphology is in-situ synthesized by employing Co foam as Co ions source and substrate through a facile solvothermal approach. The helical micro-nano structured Co-CSN possesses three-dimensional (3D) networks that formed via hydrogen bonds, which endows it structural flexibility and abundant open redox reaction sites. Based on these advantages, the as-fabricated self-supporting Co-CSN helical micro-nano rods deliver a high areal capacitance of 10.19F/cm2, a good rate capability of 76.4% when increasing the current density to 30 mA/cm2. Furthermore, the assembled asymmetric supercapacitor (ASC) yields a volumetric capacitance of 7.45F/cm3 at 3 mA/cm2 and a high energy density of 2.65 mW h cm−3. Meanwhile, the fabricated aqueous Co-CSN//Zn battery presents a high capacity of 1.37 mAh/cm2 and a remarkable energy density of 19.0 mW h cm−3. Impressively, these two devices exhibit superior cycling performance (84.8% of its initial capacitance retained for Co-CSN//AC ASC and 81.1% for Co-CSN//Zn battery after 10,000 cycles). This work demonstrates supper promising of coordination supramolecular network materials for electrochemical energy storage.

α‐MnO2‐Sensitized SrCO3−Sr(OH)2 Supported on Two‐Dimensional Carbon Composites as Stable Electrode Material for Asymmetric Supercapacitor and Oxygen Evolution Catalysis

AbstractWe developed α‐MnO2‐sensitized SrCO3−Sr(OH)2 supported on amine functionalized reduced graphene oxide (rGO) nanosheets (denoted as MSSG) to understand the energy storage and the electrocatalytic properties. Three different nanocomposites with the tuned Mn precursors such as 0.625, 1.25 and 2.5 mmol, were prepared and denoted as MSSG‐1, MSSG‐2 and MSSG‐3, respectively and loaded on the electrode's surface. Among the nanocomposites loaded electrodes, MSSG‐1 loaded electrodes exhibit a maximum specific capacitance (Csp) of 792 F/g at 3.5 A/g current density and is morphologically stable even after 5000 cycles with a retention level of 95.9 %. With this outcome, the assembled asymmetric supercapacitor (AASC) device is mechanized effectively to power the light emitting diodes (LEDs) for 62 s continuously. In addition, the prepared electrode materials were examined for oxygen evolution reaction (OER) for enhanced electrocatalytic performance with low overpotential (346 mV at 10 mA cm−2 current density) and Tafel slope (97 mV Dec−1). In addition, the long‐term durability study represents a stable performance of the loaded electrode lasting up to 72 h. Notably, the mesoporous nanostructures at the electrode surface offer an effective synergistic effect between SrCO3−Sr(OH)2 supported on NH2‐functionalized rGO nanosheets (SSG) and α‐MnO2.

Controllable Transformation of Metal-Organic Framework Nanosheets into Oxygen Vacancy NixCo3-xO4 Arrays for Ultrahigh-Capacitance Supercapacitors with Long Lifespan.

The amino-functionalized bimetal NH2-NiCo-MOF nanosheet array is first fabricated on Ni foam substrates and then controllably transformed into oxygen vacancy bimetal oxide arrays by simply thermal annealing in air. This NiCo-based oxide array (NixCo3-xO4/NF) achieves high capacitance (2484 F g-1 at 1 A g-1), excellent rate performance (91.4%), and long cycling life when assessed as promising electrode material for supercapacitors. Notably, the existing oxygen vacancy in NixCo3-xO4 promotes the electrochemical performance of NixCo3-xO4/NF due to the enhancement of electrical conductivity and capture capability for OH-. In addition, the assembled asymmetric supercapacitor (ASC) device exhibits an excellent energy density of 39.3 W h kg-1 at a power density of 800.2 W kg-1, which still remains 32.2 W h kg-1 even at a high power density of 7994.5 W kg-1. Furthermore, a light-emitting diode can be lightened for more than 6 min, demonstrating a great potential for practical application of ASC devices. This work knocks on the door of a feasible strategy for designing and synthesizing 2D metal oxide nanosheet arrays with excellent electrochemical properties.

NiCo-layered double hydroxide with cation vacancy defects for high-performance supercapacitors

Layered double hydroxides (LDHs) with high specific capacitances have proved to be promising electrode materials for supercapacitors. However, the drawbacks of their insulating nature and limited active sites hinder further capacity enhancement. Herein, the NiCo-LDH/NF with abundant cobalt ion vacancy defects (D-NiCo-LDH/NF) was synthesized based on the memory effect. Revealed by the density functional theory (DFT) calculations, the cobalt ion vacancy induces more active electrons to near the Fermi level, thus enhancing conductivity and accelerating charge transfer. Profiting from the optimized local electronic structure and more exposed active sites, the as-synthesized d-NiCo-LDH/NF exhibits unexpected specific capacity of 361 mAh g − 1 and specific capacitance of 3200 F g − 1 at the current density of 1 A g − 1, much higher than that of the pristine NiCo-LDH/NF electrode (282 mAh g − 1 and 2500 F g − 1 at 1 A g − 1). Furthermore, assembled asymmetric supercapacitor (ASC) with d-NiCo-LDH/NF and activated carbon (AC) working as the positive electrode and negative electrode material, respectively, displays a superior energy density of 53 Wh kg−1 under a power density of 752 W kg−1 with outstanding cycle stability of 94.7% retention after 5000 cycles.

A comprehensive study on rational design of Cu decorated Fe3O4@‎CeOHCO3 with enhanced capacitance in supercapacitor applications

In this work, a novel Cu decorated Fe3O4@ CeOHCO3 nanocomposite (Cu-Fe3O4@‎CeOHCO3) has been prepared by a one-step hydrothermal method. Fabricating into the electrode, the electrochemical properties of the prepared materials were characterized by cyclic voltammetry (CV), galvano-static charge-discharge (GCD) test and electrochemical impedance spectroscopy (EIS). The specific capacitance of the Cu-Fe3O4@ CeOHCO3 electrode was 324.7 F g−1 at a current density of 1.0 A g−1 with a capacitive retention of 88.3% after 1000 charge-discharge cycles. The assembled asymmetric supercapacitor(ASC) device can provide an energy density of 35.4 W h kg−1 with a high power density of 781.9 W kg−1. DFT calculations prove that the surface modification of Cu functions significantly in modulating the electronic structure and supercapacitive properties of CeOHCO3. Our self-assembled Cerium-based composite may initiate the suitability for energy storage devices and provides a valuable reference for the fabrication in sodium Ion supercapacitors.

Self-assembled Cobalt-doped NiMn-layered double hydroxide (LDH)/V2CTx MXene hybrids for advanced aqueous electrochemical energy storage properties

High-performance aqueous electrochemical energy storage technology has attracted extensive research interest due to its high safety and potential for commercialization. Herein, following the simultaneous doping-electrostatic synergistic assembly strategy, we synthesized the 2D/2D Co-doped NiMn-Layered double hydroxide (LDH)/V2CTx MXene (CNMV) composite materials that serve as advanced electrodes for aqueous energy storage devices, such as supercapacitors and zinc ion batteries (ZIBs). For supercapacitors, benefiting from the hetero ion doping effect, the as-assembled CNMV electrode exhibits a higher specific capacitance of 1005 F g−1 at a current density of 1 A g−1. For the assembled asymmetric supercapacitor (ASC) devices, a high energy density of 30.16 Wh kg−1 at 0.7 kW kg−1 was achieved. Acting as the cathode for ZIBs, CNMV exhibits a high reversible capacity of 322.7 mA h g−1 at 0.2 A g−1 after 100 cycles, and a considerable energy density of 368.7 W h kg−1 at a power density of 246 W kg−1. The battery-type transformation tothe pseudocapacitance-type CNMV electrode for the supercapacitor was demonstrated by quantitative kinetic analysis, while phase transformation and Zn2+ insertion/extraction for zinc ion storage mechanism were demonstrated by ex-situ XRD and XPS. This study provides a facile and effective approach for the design of high-performance MXene-based electrodes for aqueous electrochemical energy storage devices.

Facile electrodeposition of Mn3O4 nanoparticles on wood-derived porous carbon for high-performance asymmetric supercapacitor

In this study, we report a facile method of anchoring Mn3O4 nanoparticles on the surface of wood-derived porous carbon via electrodeposition to enhance the specific capacitance and cycling performance of electrodes for supercapacitors. Owing to the synergistic effect of the natural tubular porous structures of wood-derived porous carbon and the high theoretical specific capacitance of Mn3O4, wood-derived porous carbon-Mn3O4 composites (WPC-Mn3O4) deliver a high specific capacitance (315 F g−1 at the current density of 1 A g−1) and an outstanding cycling stability (91% of maximum capacitance after 10,000 cycles at 10 A g−1) in 1 M Na2SO4 electrolyte. Furthermore, the WPC-Mn3O4 and activated carbon (AC) assembled asymmetric supercapacitor (ASC) WPC-Mn3O4//AC delivers a high energy density of 34.85 Wh kg−1 at 700.0 W kg−1, demonstrating a high applicability in practical energy storage devices. The resultant WPC-Mn3O4 composites with excellent electrochemical properties are expected to be used as a potential cathode material for the development of high-performance supercapacitors.