High rate capability electrode constructed by anchoring CuCo2S4 on graphene aerogel skeleton toward quasi-solid-state supercapacitor

MnO2/Ni-Cu-Plated Polyester Fabric as a Free-Standing Electrode in Supercapacitor Applications

The main objective of this research is to investigate the electrochemical characteristics of Ni-Cu-plated polyester when MnO2 is deposited on it and serves as a flexible electrode. For this purpose, the Ni-Cu-plated polyester electrode fabrics prepared in this way were deposited with MnO2 over different immersion times. The conductive polyester electrode that was prepared underwent immersion in an aqueous solution of KMnO4 (0.1 M) for durations of 5, 10, and 30 min. The electrical resistance of the prepared samples was measured using a two-point probe technique. Additionally, the electrochemical properties of the Ni-Cu-plated polyester with MnO2 deposition were examined using a three-electrode cell setup under ambient conditions. The surface structure and elemental composition of the sample electrodes were examined with a scanning electron microscope (SEM). In this research, the asymmetric supercapacitor cell (ASC) consisting of a Ni-Cu/MnO2-deposited textile as the cathode electrode and active carbon-coated activated carbon cloth as the anode electrode was assembled. Also, the symmetric supercapacitor cell (SSC) using Ni-Cu/MnO2 deposited polyester as both the anode and cathode was assembled. Cyclic voltammetry (CV), galvanostatic charging-discharging (GCD), and electrochemical impedance spectroscopy (EIS) measurements were utilized to assess and compare the electrochemical performance. The areal specific capacitances of the ASC at current densities of 2, 4, 8, and 16 mA cm-2 were calculated to be 558.6, 481.9, 435.5, and 330 mF cm-2, respectively. In comparison, the achieved storage results related to ASC are far higher than those of SSC. The results are discussed in the text in detail.

Enhanced visible light driven photodegradation of rifampicin and Cr(VI) reduction activity of ultra-thin ZnO nanosheets/CuCo2S4QDs: A mechanistic insights, degradation pathway and toxicity assessment

In this study, we focused on fabrication of porous ultra-thin ZnO nanosheet (PUNs)/CuCo2S4 quantum dots (CCS QDs) for visible light-driven photodegradation of rifampicin (RIF) and Cr(VI) reduction. The morphology, structural, optical and textural properties of fabricated photocatalyst were critically analyzed with different analytical and spectroscopic techniques. An exceptionally high RIF degradation (99.97%) and maximum hexavalent Cr(VI) reduction (96.17%) under visible light was achieved at 10 wt% CCS QDs loaded ZnO, which is 213% and 517% greater than bare ZnO PUNs. This enhancement attributed to the improved visible light absorption, interfacial synergistic effect, and high surface-rich active sites. Extremely high generation of ●OH attributed to the spin-orbit coupling in ZnO PUNs@CCS QDs and the existence of oxygen vacancies. Besides, the ZnOPUNs@CCS QDs, forming Z-scheme heterojunctions, enhanced the separation of photogenerated charge carriers. We investigated the influencing factors such as pH, inorganic ions, catalyst dosage and drug dosage on the degradation process. More impressively, a stable performance of ZnO PUNs@CCS QDs obtained even after six consecutive degradation (85.9%) and Cr(VI) reduction (67.7%) cycles. Furthermore, the toxicity of intermediates produced during the photodegradation process were assessed using ECOSAR program. This work provides a new strategy for ZnO-based photocatalysis as a promising candidate for the treatment of various contaminants present in water bodies.

Construction of Ti3C2Tx MXene wrapped urchin-like CuCo2S4 microspheres for high-performance asymmetric supercapacitors

Copper cobalt sulfide (CuCo₂S₄) nanomaterials are regarded as promising electrode materials for high-performance supercapacitors due to their abundant redox states and considerable theoretical capacities. However, the intrinsic poor electrical conductivity, sluggish reaction kinetics and insufficient number of electroactive sites of these materials are huge barriers to realize their practical applications. In this study, a facile two-step strategy to engineer a hierarchical 3D porous CuCo₂S₄/MXene composite electrode is presented for enhanced storage properties. This well-constructed CuCo₂S₄/MXene composite not only provides abundant active sites for the faradaic reaction, but also offers more efficient pathways for rapid electron/ion transport and restricts the volumetric expansion during the charge/discharge process. When evaluated in a 3 M KOH electrolyte, the CuCo₂S₄/MXene-3 electrode exhibits a specific capacity of 1351.6 C g^-1 at 1 A g^-1 while retaining excellent cycling stability (95.2% capacity retention at 6 A g^-1 after 10 000 cycles). Additionally, the solid-state asymmetric supercapacitor (ASC) CuCo₂S₄/MXene//AC device displays an energy density of 78.1 W h kg^-1 and a power density of 800.7 W kg^-1. Two ASC devices connected in series can illuminate a blue LED indicator for more than 20 min, demonstrating promising prospects for practical applications. These electrochemical properties indicate that the high-performance CuCo₂S₄/MXene composites are promising electrode materials for advanced asymmetric supercapacitors.

Highly stable, stretchable, and versatile electrodes by coupling of NiCoS nanosheets with metallic networks for flexible electronics

The rapid development of portable electronics has contributed to an urgent demand for versatile and flexible electrodes of wearable energy storage devices and pressure sensors. We fabricate a stretchable electrode by coupling the nickel-cobalt sulfide (NiCoS) nanosheet layer with Ag@NiCo nanowire (NW) networks. NiCoS wrinkled nanostructure, highly conductive networks, and intense interactions between substrate/networks and active materials/networks endow the electrodes with excellent energy storage capacity, superior electrochemical/mechanical stability, and good conductivity. A high-performance asymmetric supercapacitor is developed using the composite electrode. It operates in a wide potential window of 1.4 V and achieves a maximum energy density of 40.0 W h kg^-1 at a power density of 1.1 kW kg^-1; it also exhibits excellent mechanical flexibility and good waterproof performance. Moreover, a sandwiched capacitive pressure sensor constructed using the same electrodes has a wide sensing range (up to 260 kPa), low detection limit (∼47 mN), fast response (∼66 ms), and excellent mechanical stability (10 000 cycles). This study demonstrates that the appropriate design of the functional electrode facilitates the construction of various high-performance devices, denoting the versatility of our electrodes in the development of wearable electronics.

High-rate transition metal-based cathode materials for battery-supercapacitor hybrid devices

With the rapid development of portable electronic devices, electric vehicles and large-scale grid energy storage devices, there is a need to enhance the specific energy density and specific power density of related electrochemical devices to meet the fast-growing requirements of energy storage. Battery-supercapacitor hybrid devices (BSHDs), combining the high-energy-density feature of batteries and the high-power-density properties of supercapacitors, have attracted mass attention in terms of energy storage. However, the electrochemical performances of cathode materials for BSHDs are severely limited by poor electrical conductivity and ion transport kinetics. As the rich redox reactions induced by transition metal compounds are able to offer high specific capacity, they are an ideal choice of cathode materials. Therefore, this paper reviews the currently advanced progress of transition metal compound-based cathodes with high-rate performance in BSHDs. We discuss some efficient strategies of enhancing the rate performance of transition metal compounds, including developing intrinsic electrode materials with high conductivity and fast ion transport; modifying materials, such as inserting defects and doping; building composite structures and 3D nano-array structures; interfacial engineering and catalytic effects. Finally, some suggestions are proposed for the potential development of cathodes for BSHDs, which may provide a reference for significant progress in the future.

A high-performance asymmetric supercapacitor-based (CuCo)Se2/GA cathode and FeSe2/GA anode with enhanced kinetics matching

The performance of asymmetric supercapacitors (ASCs) is limited by the poorly matched electrochemical kinetics of available electrode materials, which generally results in reduced energy density and inadequate voltage utilization. Herein, a porous conductive graphene aerogel (GA) scaffold was decorated with copper cobalt selenide ((CuCo)Se₂) or iron selenide (FeSe₂) to construct positive and negative electrodes, respectively. The (CuCo)Se₂/GA and FeSe₂/GA electrodes exhibited high specific capacitances of 672 and 940 F g^-1, respectively, at 1 A g^-1. The capacitance contributions from the Co³⁺/Co₂⁺ and Fe³⁺/Fe²⁺ redox couple for the positive and negative electrodes were determined to elucidate the energy storage mechanism. Furthermore, the kinetics study of the two electrodes was performed, revealing b values ranging between 0.7 and 1 at various scan rates and demonstrating that the surface-controlled processes played the dominant role, leading to fast charge storage capability for both electrodes. Fabrication of an ASC device with a configuration of (CuCo)Se₂/GA//FeSe₂/GA resulted in a voltage of 1.6 V, a high energy density of 39 W h kg^-1, and a power density of 702 W kg^-1. The excellent electrochemical performances of the (CuCo)Se₂/GA and FeSe₂/GA electrodes demonstrate their potential applications in energy storage devices.

Copper niobate nanowires immobilized on reduced graphene oxide nanosheets as rate capability anode for lithium ion capacitor

Binary metal niobium oxides can offer a higher specific capacity compared to niobium pentoxide (Nb₂O₅) and thus are ideal anode candidates for lithium ion capacitors (LICs). However, their lower electronic conductivity limits their ability to achieve high energy and power densities. In this paper, one-dimensional (1D) copper niobate (CuNb₂O₆) nanowires are successfully prepared by electrospinning technology and then immobilized on two-dimensional (2D) reduced graphene oxide (rGO) nanosheets to form a unique 1D nanowire/2D nanosheet CuNb₂O₆/rGO structure. The 1D/2D CuNb₂O₆/rGO electrode exhibits a high specific capacity of 312.2 mAh g^-1 at 100 mA g^-1 as the anode of LICs. The proposed Li⁺ storage mechanism of the CuNb₂O₆ anode involves CuNb₂O₆ decomposition into lithium niobate (Li₃NbO₄) and copper (Cu) during the initial lithium insertion process. The intercalation-type Li₃NbO₄ will further serve as the host to Li⁺ and the inactive Cu phase will act as a conductive network for electron transportation. Furthermore, the energy density of the assembled CuNb₂O₆/rGO//activated carbon (CuNb₂O₆/rGO//AC) device could achieve a value as high as 92.1 Wh kg^-1 and could thus be considered as a possible alternative electrode material for high energy and power LICs.

In Situ Coating of Li7P3S11 Electrolyte on CuCo2S4/Graphene Nanocomposite as a High-Performance Cathode for All-Solid-State Lithium Batteries

A cathode material, CuCo₂S₄/graphene@10%Li₇P₃S₁₁, is reported for all-solid-state lithium batteries with high performance. The electrical conductivity of CuCo₂S₄ is improved by compounding with graphene. Meanwhile, Li₇P₃S₁₁ electrolyte is coated on the surface of CuCo₂S₄/graphene nanosheets to build an intimate contact interface between the solid electrolyte and the electrode effectively, facilitating lithium-ion conduction. Benefitting from the balanced and efficient electronic and ionic conductions, all-solid-state lithium batteries using CuCo₂S₄/graphene@10%Li₇P₃S₁₁ composite as cathode materials demonstrate superior cycling stability and rate capabilities, exhibiting an initial discharge specific capacity of 1102.25 mAh g^-1 at 50 mA g^-1 and reversible capacity of 556.41 mAh g^-1 at a high current density of 500 mA g^-1 after 100 cycles. These results demonstrate that the CuCo₂S₄/graphene@10%Li₇P₃S₁₁ nanocomposite is a promising active material for all-solid-state lithium batteries with superior performances.

Freestanding Needle Flower Structure CuCo2S4 on Carbon Cloth for Flexible High Energy Supercapacitors With the Gel Electrolyte

A facile hydrothermal approach was adopted to the direct synthesis of bimetallic sulfide (CuCo₂S₄) on carbon cloth (CC) without binders for the supercapacitor's electrodes. A possible formation mechanism was proposed. The prepared bimetallic electrode exhibited a high specific capacitance (Csp) of 1,312 F·g⁻¹ at 1 A·g⁻¹, and an excellent capacitance retention of 94% at 5 A·g⁻¹ over 5,000 cycles. In addition, the asymmetric supercapacitor (CuCo₂S₄/CC//AC/CC) exhibited energy density (42.9 wh·kg⁻¹ at 0.8 kW·kg⁻¹) and outstanding cycle performance (80% initial capacity retention after 5,000 cycles at 10 A·g⁻¹). It should be noted that the electrochemical performance of a supercapacitor device is quite stable at different bending angles. Two charged devices in series can light 28 red-colored LEDs (2.0 V) for 5 min. All of this serves to indicate the potentially high application value of CuCo₂S₄.

Supercapacitive Performances of Ternary CuCo2S4 Sulfides

Currently, ternary CuCo₂S₄ sulfides are intensively investigated as electrode materials for electrochemical capacitors due to their low cost, high conductivity, and synergistic effect. The research of CuCo₂S₄ materials for energy storage has gradually grown from 2016. The supercapacitive performances of CuCo₂S₄ electrodes for electrochemical capacitors are briefly reviewed in this work. The structure, morphology, and particle size of CuCo₂S₄ are related to the synthesis conditions and electrochemical performances. The thin films of CuCo₂S₄ nanostructures deposited on conductive substrates and their composites both show better properties than single CuCo₂S₄. CuCo₂S₄ and its composites reveal large potential for asymmetric capacitors, delivering high energy densities. However, there is still much new space remaining for future research. The possible development directions, challenges, and opportunities for CuCo₂S₄ materials are also discussed.

Sea urchin-like CuCo2S4 microspheres with a controllable interior structure as advanced electrode materials for high-performance supercapacitors

The rational construction of a supercapacitor electrode structure can realize high specific surface area, good cycling stability and high capacitance.

Synthesis of single-phase CuCo2-xNixS4 for high-performance supercapacitors

Developing safe, efficient and environment-friendly energy storage systems continues to inspire researchers to synthesize new electrode materials. Doping or substituting host material by some guest elements has been regarded as an effective way to improve the performance of supercapacitors. In this work, single-phase CuCo_2-xNi_xS₄ materials were synthesized by a facile two-step hydrothermal method, where Co in CuCo₂S₄ was substituted by Ni. Cobalt could be easily substituted with Ni in a rational range to keep its constant phase. But, a high content of Ni resulted in a multi-phase composite. Among a series of CuCo_2-xNi_xS₄ materials with different Ni/Co mole ratios, CuCo_1.25Ni_0.75S₄ material presented a significantly high specific capacitance (647 F g^-1 or 272 C g^-1 at 1 A g^-1) and the best cycling stability (∼98% specific capacitance retention after 10,000 charge-discharge cycles), which was mainly due to the modified composition, specific single phase, higher electroconductivity, more electroactive sites and the synergistic effect between Ni and Co. Moreover, the assembled asymmetric capacitor using CuCo_1.25Ni_0.75S₄ as a positive electrode and activated carbon as a negative electrode delivered a high energy density of 31.8 Wh kg^-1 at the power density of 412.5 W kg^-1. These results demonstrated that ternary metal sulfides of CuCo_2-xNi_xS₄ are promising electrode materials for high-performance supercapacitors.

Recent Advances of Porous Graphene: Synthesis, Functionalization, and Electrochemical Applications

Graphene is a 2D sheet of sp² bonded carbon atoms and tends to aggregate together, due to the strong π-π stacking and van der Waals attraction between different layers. Its unique properties such as a high specific surface area and a fast mass transport rate are severely blocked. To address these issues, various kinds of 2D holey graphene and 3D porous graphene are either self-assembled from graphene layers or fabricated using graphene related materials such as graphene oxide and reduced graphene oxide. Porous graphene not only possesses unique pore structures, but also introduces abundant exposed edges and accelerates mass transfer. The properties and applications of these porous graphenes and their composites/hybrids have been extensively studied in recent years. Herein, recent progress and achievements in synthesis and functionalization of various 2D holey graphene and 3D porous graphene are reviewed. Of special interest, electrochemical applications of porous graphene and its hybrids in the fields of electrochemical sensing, electrocatalysis, and electrochemical energy storage, are highlighted. As the closing remarks, the challenges and opportunities for the future research of porous graphene and its composites are discussed and outlined.

Wrapping CuCo2S4 arrays on nickel foam with Ni2(CO3)(OH)2 nanosheets as a high-performance faradaic electrode

Ternary metal sulfides represent a new class of faradaic electrode material outperforming their oxide counterparts.