In Situ Generation of Vertically Crossed P-Cu3Se2 Ultrathin Nanosheets Derived from Cu2S Nanorod Arrays for High-Performance Supercapacitors

In situ synthesis of bimetallic chalcogenides with highly conductive carbon nanotubes for efficient symmetric hybrid supercapacitors

Achieving high energy density and long cycle stability in energy storage devices necessitates excellent electrochemical performance, which often relies on the innovative structural design of the materials under investigation. Therefore, hybrid supercapacitors are crucial in the realm of energy storage devices. The elevated energy and power densities, combined with various energy storage mechanisms, significantly improve electrochemical performance. Here, we developed a highly efficient electrode material, carbon nanotube-metal chalcogenides (CNT-CuNiSe2), using a simple one-pot reflux method (in situ). The enhanced energy storage performance was achieved by synergising CuNiSe2 with the pi-cloud of CNTs, resulting in enhanced specific capacitance retention over prolonged cycling stability. The hybrid supercapacitor electrode was formed by combining conducting carbon cloth (CC) with CNT-CuNiSe2 as a hybrid material, referred to as the CC/CNT-CuNiSe2 material. The fabricated hybrid electrode materials demonstrated excellent potential for energy storage. CC/CNT-CuNiSe2 exhibited excellent energy storage capabilities, achieving a specific capacitance of 957.06 F g-1 at 1 A g-1. Hybrid supercapacitors with high energy and power density were developed using conducting carbon cloth and CNT-CuNiSe2, designated as CC/CNT-CuNiSe2//CC/CNT-CuNiSe2. The hybrid capacitor device demonstrated a capacitance of 265.586 F g-1, along with an energy density of 82.99 W h kg-1 at a power density of 1511.35 W kg-1. When charged and discharged at 4 A g-1, the hybrid capacitor device displayed an impressive capacitance retention of 101.3% over 6000 continuous cycles.

Reinforced supercapacitor electrode via reduced graphene oxide encapsulated NiTe2-FeTe2 hollow nanorods

Metal telluride-based nanomaterials have garnered considerable interest as positive electrode materials for supercapacitors due to their plentiful redox-active sites, robust chemical stability, and excellent electrical conductivity. In this work, these advantageous properties are further enhanced by hybridizing NiTe2-FeTe2 (NFT) hollow nanorods with reduced graphene oxide (RGO), resulting in an NFT@RGO composite suitable for supercapacitor applications. The hollow rod-like structure promotes efficient ion diffusion and maximizes the exposure of electroactive sites, while the RGO network boosts conductivity and mitigates nanomaterial agglomeration, thus preserving structural integrity and prolonging material durability. The NFT@RGO-based electrode exhibits a notable capacity of 1388.5 C g-1 at 1 A g-1, with 93.82% capacity retention after 10 000 cycles. This remarkable performance arises from the synergistic contributions of the Ni and Fe metals, the electrically conductive Te element, the RGO framework, and the unique hollow morphology of the nanorods. Furthermore, a hybrid device employing activated carbon (AC) as the negative electrode (NFT@RGO//AC) achieves an energy density of 61.11 W h kg-1 and retains 89.85% of its capacity over 10 000 cycles, underscoring the promise of NFT@RGO for next-generation supercapacitors. These findings position the designed nanomaterial as an excellent candidate for high-performance energy storage systems.

Porous nickel-cobalt phosphate with oxygen-rich vacancies in situ grown on dopamine-modified cellulose textiles as self-supporting high mass loadings supercapacitor electrode

Transition-metal phosphates/phosphides showcase significant promise for energy-related applications because of their high theoretical electrochemical characteristics. However, sluggish electro/ion transfer rates and kinetically unfavorable reaction sites hinder their application at high mass loading. Herein, a self-supporting electrode based on transition-metal phosphates was successfully fabricated via a one-step electrodeposition process. The nanosheet structure of transition-metal phosphates, formed by interconnecting nanoparticles, effectively mitigates the impact of stress and achieves a high mass-loading (21 mg cm-2) of the electrode. Additionally, the oxygen vacancy-rich and porous nanostructure of transition-metal phosphates endows the as-prepared electrodes with a significantly increased conductivity and fast ion migration rate for enhancing electrochemical kinetics. Consequently, the as-fabricated transition-metal phosphate electrode displays the highest areal specific capacity of 39.2F cm-2. Furthermore, the asymmetric supercapacitor achieves a maximum energy density of 0.79 mWh cm-2 and a high capacity retention of 93.0 % for 10000 cycles under 60 mA cm-2. This work provides an ideal strategy for fabricating flexible electrodes with high mass loading and synthesizing transition-metal phosphate electrodes rich in oxygen vacancies.

Cu2S/C@NiMnCe-layered double hydroxide with core-shell rods array structure as the cathode for high performance supercapacitors

The selection of highly efficient materials and the construction of advantageous structures are essential for realizing high-performance electrode materials. In this paper, electrode material Cu2S/C@NiMnCe-LDH/CF with excellent morphology and high performance has been successfully designed and prepared by simple hydrothermal and calcination techniques. First, ZIF-67 is loaded on the outer layer of Cu2S rods to obtain core-shell structured Cu2S@ZIF-67 rods, whose ZIF-67 MOF shell is carbonized to obtain Cu2S@C rods. Then, NiMnCe-LDH are epitaxially loaded on the outer layer of Cu2S@C to obtain Cu2S/C@NiMnCe-LDH rods. At a current density of 2 mA cm-2, Cu2S/C@NiMnCe-LDH/CF exhibits an area capacitance of 5176.4 mF cm-2. The mass capacitance and the energy density of the Cu2S/C@NiMnCe-LDH/CF//AC asymmetric supercapacitor (ASC) reach 150.82F g-1 at a sweep rate of 0.8 A/g and 53.62 Wh kg-1 at a power density of 639.99 W kg-1, respectively. Meanwhile, after 8000 electrochemical cycles, the specific capacitance of Cu2S/C@NiMnCe-LDH/CF//AC still has a retention rate of 86.32 %, which proves its excellent cycling stability. These results demonstrate a new strategy for the preparation of novel core-shell structured Cu2S/C@NiMnCe-LDH/CF nanocomposite material for electrode materials of energy storage devices with superb performance.

Stepwise Construction of MoS2@CoAl-LDH/NF 3D Core-Shell Nanoarrays with High Hole Mobility for High-Performance Asymmetric Supercapacitors

Supercapacitors (SCs) have received widespread attention as excellent energy storage devices, and the design of multicomponent electrode materials and the construction of ingenious structures are the keys to enhancing the performance of SCs. In this paper, MoS2 nanorods were used as the carrier structure to induce the anchoring of CoAl-LDH nanosheets and grow on the surface of nickel foam (NF) in situ, thus obtaining a uniformly distributed MoS2 nanorod@CoAl-LDH nanosheet core-shell nanoarray material (MoS2@CoAl-LDH/NF). On the one hand, the nanorod-structured MoS2 as the core provides high conductivity and support, accelerates electron transfer, and avoids agglomeration of CoAl-LDH nanosheets. On the other hand, CoAl-LDH nanosheet arrays have abundant interfacially active sites, which accelerate the electrolyte penetration and enhance the electrochemical activity. The synergistic effect of the two components and the unique core-shell nanostructure give MoS2@CoAl-LDH/NF a high capacity (14,888.8 mF cm-2 at 2 mA cm-2) and long-term cycling performance (104.4% retention after 5000 charge/discharge cycles). The integrated MoS2@CoAl-LDH/NF//AC device boasts a voltage range spanning from 0 to 1.5 V, achieving a peak energy density of 0.19 mW h cm-2 at 1.5 mW cm-2. Impressively, it maintains a capacitance retention rate of 84.6% after enduring 10,000 cycles, demonstrating exceptional durability and stability.

In situ selective selenization of ZIF-derived CoSe2 nanoparticles on NiMn-layered double hydroxide@CuBr2 heterostructures for high performance supercapacitors

As an emerging energy storage device, the practical application of supercapacitors (SCs) is currently constrained by their low energy density. Enhancing the capacitance of supercapacitors by leveraging the synergistic effect of multiple components in composite electrodes with well-designed structures can effectively increase their energy density. Here, a wire-sheet-particle hierarchical heterostructured CoSe2@NiMn-layered double hydroxide (NiMn-LDH) @Cu1.8Se/Copper foam (CF) electrode is synthesized via phase pseudomorphic transformation process achieved by selective selenization for Cu and Co elements. Benefiting from the stable support structure of CuBr2, the large specific surface area of NiMn-LDH, and the excellent conductivity of CoSe2, the prepared binder-free electrode shows excellent electrochemical properties. The CoSe2@NiMn-LDH@Cu1.8Se hybrid electrode exhibits a superior specific areal capacitance of 7064 mF cm-2 at 2 mA cm-2 and a stable cyclic performance with 80.11 % capacitance retention after 10,000 cycles. Furthermore, the assembled CoSe2@NiMn-LDH@Cu1.8Se/CF//AC (activated carbon) asymmetric supercapacitor (ASC) achieves an energy density of 36.6 Wh kg-1 when the power density is 760.6 W Kg-1 and retains 87.35 % of the initial capacitance after 5000 cycles. Overall, this pioneering research provided new insight for preparing supercapacitor electrode materials by selective selenization and ration design of the structures.

In situ growth of a redox-active metal-organic framework on electrospun carbon nanofibers as a free-standing electrode for flexible energy storage devices

The rational construction of free-standing and flexible electrodes for application in electrochemical energy storage devices and next-generation supercapacitors is an emerging research focus. Herein, we prepared a redox-active ferrocene dicarboxylic acid (Fc)-based nickel metal-organic framework (MOF) on electrospun carbon nanofibers (NiFc-MOF@CNFs) via an in situ approach. This in situ approach avoided the aggregation of the MOF. The NiFc-MOF@CNF flexible electrode showed a high redox-active behavior owing to the presence of ferrocene and flexible carbon nanofibers, which led to unique properties, including high flexibility and lightweight. Furthermore, the prepared electrode was utilized in a supercapacitors (SC) without the use of any binder, which achieved a specific capacity of 460 C g-1 at 1 A g-1 with an excellent cyclic retention of 82.2% after 25 000 cycles and a good rate capability. A flexible asymmetric supercapacitor device was assembled, which delivered a high energy density of 56.25 W h kg-1 and a long-lasting cycling performance. Also, the prepared electrode could be used as a freestanding electrode in flexible devices at different bending angles. The obtained cyclic voltammetry curves showed negligible changes, indicating the high stability and good flexibility of the electrode. Thus, the use of the in situ strategy can lead to the uniform growth of redox-active MOFs or other porous materials on CNFs.

Flexible All-Solid-State Asymmetric Supercapacitors Based on PPy-Decorated SrFeO3-δ Perovskites on Carbon Cloth

The defective structure and high oxygen vacancy concentration of SrFeO3-δ perovskite enable fast ion-electron transport, but its low conductivity still hinders the high electrochemical performance. Herein, to enhance the conductivity of SrFeO3-δ-based electrodes, polypyrrole-modified SrFeO3-δ perovskite on carbon cloth (PPy@SFO@CC) has been successfully fabricated by electrodeposition of polypyrrole (PPy) on the surface of SFO@CC. The optimal PPy700@SFO@CC electrode exhibits a specific capacitance of 421 F g-1 at 1 A g-1. It was found that the outside PPy layer not only accelerates the electron transport and ion diffusion but also creates more oxygen vacancies in SrFeO3-δ, enhancing the charge storage performance significantly. Moreover, the NiCo2O4@CC//PPy700@SFO@CC device maintains a specific capacitance of 63.6% after 3000 cycles, which is ascribed to the weak adhesion forces between the active materials and carbon cloth. Finally, the all-solid-state flexible supercapacitor NiCo2O4@CC//PPy700@SFO@CC is constructed with PVA-KOH as the solid electrolyte, delivering an energy density of 16.9 W h kg-1 at a power density of 984 W kg-1. The flexible supercapacitor retains 69% of its specific capacitance after 1000 bending and folding times, demonstrating a certain degree of foldability. The present study opens new avenues for perovskite oxide-based flexible all-solid-state supercapacitors.

Directly Sputtered Molybdenum Disulfide Nanoworms Decorated with Binder-less VN and W2N Nanoarrays for Bendable Large-Scale Asymmetric Supercapacitor

Considering the superior capacitive performance and rich redox kinetics, the two-dimensional (2D) layered molybdenum disulfide (MoS2) and transition metal nitrides (TMNs) have emerged as the latest set of nanomaterials. Direct incorporation of key materials vanadium nitride (VN) and tungsten nitride (W2N) into a MoS2 array has been achieved on cost-effective, bendable stainless steel (SS) foil via a reactive cosputtering route. Herein, we have utilized the synergistic effect of intermixed nanohybrids to develop a flexible asymmetric supercapacitor (FASC) device from MoS2-VN@SS (negative) and MoS2-W2N@SS (positive) electrodes. As-constructed FASC cell possesses a maximum operational potential of 1.80 V and an exceptional gravimetric capacitance of 200 F g-1 at a sweep rate of 5 mV s-1. The sustained capacitive performance mainly accounts for the synergism induced through unique interfacial surface architecture provided by MoS2 nanoworms and TMN conductive hosts. The sulfur and nitrogen edges ensure the transport channels to Li+/SO4-2 ions for intercalation/deintercalation into the composite nanostructured thin film, further promoting the pseudocapacitive behavior. Consequently, the supercapacitor cell exhibits a distinctive specific energy of 87.91 Wh kg-1 at 0.87 kW kg-1 specific power and a reduced open circuit potential (OCP) decay rate (∼42% self-discharge after 60 min). Moreover, the assembled flexible device exhibits nearly unperturbed electrochemical response even at bending at 165° angle and illustrates a commendable cyclic life-span of 82% after 20,000 charge-discharge cycles, elucidating advanced mechanical robustness and capacitance retentivity. The powering of a multicolor light-emitting diode (LED) and electronic digital watch facilitates the practical evidence to open up possibilities in next-generation state-of-the-art wearable and miniaturized energy storage systems.

Constructing nickel sulfide @ nickel boride hybrid nanosheet arrays with crystalline/amorphous interfaces for supercapacitors

Designing a heterostructure with unique morphology and nanoarchitecture is regarded as an efficient strategy to achieve high-energy-density supercapacitors (SCs). Herein, a rational nickel sulfide @ nickel boride (Ni9S8@Ni2B) heterostructure is in situ synthesized on carbon cloth (CC) substrate via a simple electrodepositon strategy followed by a chemical reduction method. The three-dimensional hierarchically porous Ni9S8@Ni2B nanosheet arrays, consisting of crystalline Ni9S8 nanosheets and amorphous Ni2B nanosheets, can expose ample electroactive centers, shorten ion diffusion distance, and buffer volume changes during charging/discharging process. More importantly, the generation of crystalline/amorphous interfaces in the Ni9S8@Ni2B composite modulates its electrical structure and improves electrical conductivity. Owing to the synergy of Ni9S8 and Ni2B, the as-synthesized Ni9S8@Ni2B electrode acquires a specific capacity of 901.2C g-1 at 1 A g-1, a sound rate capability (68.3% at 20 A g-1), along with good cycling performance (79.7% capacity retention over 5000 cycles). Additionally, the assembled Ni9S8@Ni2B//porous carbon asymmetric supercapacitor (ASC) exhibits a cell voltage of 1.6 V and a maximum energy density of 59.7 Wh kg-1 at 805.2 W kg-1. These findings might offer a simple and innovative approach to fabricate advanced electrode materials for high-performance energy storage systems.

Phosphorization Engineering on a MOF-Derived Metal Phosphide Heterostructure (Cu/Cu3P@NC) as an Electrode for Enhanced Supercapacitor Performance

A highly conductive and rationally constructed metal-organic framework (MOF)-derived metal phosphide with a carbonaceous nanostructure is a meticulous architecture toward the development of electrode materials for energy storage devices. Herein, we report a facile strategy to design and construct a new three-dimensional (3D) Cu-MOF via a solvent diffusion method at ambient temperature, which was authenticated by a single-crystal X-ray diffraction study, revealing a novel topology of (2,4,7)-connected three-nodal net named smm4. Nevertheless, the poor conductivity of pristine MOFs is a major bottleneck hindering their capacitance. To overcome this, we demonstrated an MOF-derived Cu3P/Cu@NC heterostructure via low-temperature phosphorization of Cu-MOF. The electronic and ionic diffusion kinetics in Cu3P/Cu@NC were improved due to the synergistic effects of the heterostructure. The as-prepared Cu3P/Cu@NC heterostructure electrode delivers a specific capacity of 540 C g-1 at 1 A g-1 with outstanding rate performance (190 C g-1 at 20 A g-1) and cycle stability (91% capacity retention after 10,000 cycles). Moreover, the assembled asymmetric solid-state supercapacitor (ASC) achieved a high energy density/power density of 45.5 Wh kg-1/7.98 kW kg-1 with a wide operating voltage (1.6 V). Long-term stable capacity retention (87.2%) was accomplished after 5000 cycles. These robust electrochemical performances suggest that the Cu3P/Cu@NC heterostructure is a suitable electrode material for supercapacitor applications.