As-assembled Device Research Articles

Dual-Mode Semiconductor Device Enabling Optoelectronic Detection and Neuromorphic Processing with Extended Spectral Responsivity.

High-performance semiconductor devices capable of multiple functions are pivotal in meeting the challenges of miniaturization and integration in advanced technologies. Despite the inherent difficulties of incorporating dual functionality within a single device, a high-performance, dual-mode device is reported. This device integrates an ultra-thin Al2O3 passivation layer with a PbS/Si hybrid heterojunction, which can simultaneously enable optoelectronic detection and neuromorphic operation. In mode 1, the device efficiently separates photo-generated electron-hole pairs, exhibiting an ultra-wide spectral response from ultraviolet (265nm) to near-infrared (1650nm) wavelengths. It also reproduces high-quality images of 256×256 pixels, achieving a Q-value as low as 0.00437µWcm- 2 at a light intensity of 8.58µWcm- 2. Meanwhile, when in mode 2, the as-assembled device with typical persistent photoconductivity (PPC) behavior can act as a neuromorphic device, which can achieve 96.5% accuracy in classifying standard digits underscoring its efficacy in temporal information processing. It is believed that the present dual-function devices potentially advance the multifunctionality and miniaturization of chips for intelligence applications.

Green synthesis of MnO2 via plant extracts and its composite with exfoliated graphene for high-performance asymmetric supercapacitors

Pure MnO2 nanostructure oxides were synthesized by a green synthesis method using purified natural extracts of watercress (MW) and spinach (MS) as benign and economical reducing agents for KMnO4. The MnO2/graphene composites (GMW and GMS) were prepared through a physical mixing process, in which MnO2 oxide was uniformly loaded on graphene sheets. The composition, morphology, and microstructure of the as-prepared oxides and composites were characterized using X-ray diffraction (XRD), Thermal gravimetric analysis (TGA), Raman, Scanning electron microscope (SEM), and Transmission electron microscope (TEM). Additionally, the supercapacitive performance was examined by electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and galvanostatic charge/discharge (GCD). The results imply that the composites GMS and GMW exhibit specific capacitances of 334 and 500 F/g at 1 A/g, respectively, and GMW shows a capacitance retention of 71 % after 7000 cycles at 200 mV/s. Herein, the charge storage mechanism in MnO2/graphene composites is discussed in detail. An asymmetric supercapacitor (ASC) was assembled using the GMW composite and graphene as positive and negative electrodes, respectively. The as-assembled ASC device GMW//GE was scanned reversibly at a voltage of 0–1.8 V and showed a specific capacitance of 167 F/g at 0.5 A/g with a rate capability of 77 % (128.3 F/g at 5 A/g). Moreover, the ASC exhibited excellent cycle stability of 94 % after 2000 cycles and an energy density of 18.9 Wh/kg at a power density of 2.25 kW/kg. These encouraging results showed enormous potential in developing supercapacitors with enhanced performance for practical applications.

Overall upgrading Zn-ion storage capability by engineering N/O co-doped hydrophilic hierarchical porous carbon

The couple of supercapacitors' high power density and batteries' high energy density endows aqueous zinc-ion hybrid supercapacitors (ZIHSCs) a perspective candidate for next-generation energy storage devices. Biomass-derived hierarchical porous carbon with excellent wettability towards aqueous electrolyte is regarded as a promising cathode for ZIHSCs applications. Herein, a N/O co-doped hydrophilic carbon with hierarchical porous architecture is conversed from protein enriched recycled badminton feathers via a facile and scalable strategy. The resultant carbon presents hierarchical porous architecture with high surface area and mesopore-governed pore size distribution, rich dual-doping of N/O heteroatoms and good water wetting behavior. The all-round teamwork of these unique properties provides numerous interfacial active sites plus extra reversible redox reaction for high energy density, and speedy kinetics for high power density. Incredibly, as-assembled ZIHSC device displays an ultrahigh capacity of 225.3 mAh g−1 at 0.1 A g−1 with an appreciable capacity retention of 73.8 mAh g−1 even at a 1000-fold amplified current density, thereby delivering admirable energy and power densities of 201.4 Wh kg−1 and 83.6 kW kg−1. Most satisfyingly, an ultralong cycling life with no loss in capacity is achieved after 40,000 cycles even at 50 A g−1. Therefore, by taking advantage of its intrinsic component, the conversion of biomass waste to high performance carbon-based cathode material holds a broad prospect and practical significance.

Synthesis effect on surface functionalized Ti3C2Tx MXene supported nickel oxide nanocomposites with enhanced specific capacity for supercapacitor application

Rich surface functionalization and active electrolyte-accessible supercapacitors are considered promising tools for enhanced energy storage capacity due to their high specific capacity and simple construction. One of the challenges in technical applications of recently developed MXene is that it causes phase transition and structural decomposition over time without delamination. Thus, a simple but effective method for increasing the stability of exfoliated MXene (Ti3C2Tx) by passivating exposed edges with Tetramethyl Ammonium Hydroxide (TMAOH) has been adopted here. In this work, we performed this delaminated MXene (DLMX) supported Nickel oxide (NiO) by three different synthesizing routes for composite preparation which have been thoroughly discussed. Bath Sonication assisted DLMX/NiO was found to increase oxygen-containing surface functionalities, surface area, and uniform delivery of partner composite, enhancing the electrochemical properties compared to Solvothermal and in situ-delamination synthesis. At a current density of 1 A/g, the fabricated electrode material exhibited a maximum capacity of 770C/g. After 3500 cycles a remarkable cycling performance of 97.2 % capacity retention and reached 88.1 % after 5000 cycles at 8 A/g current density. The as-assembled supercapacitor device has an energy density of up to 73 Wh kg−1 and a power density of 900 W kg−1 signifying an excellent device prospect, making them more practicable for marketable devices for advanced energy storage applications.

1.89 $ kg-1 Lake-Water-Based Semisolid Electrolytes for Highly Efficient Energy Storage.

Solid electrolytes with fast ion kinetics and superior mechanical properties are critical to electrochemical energy devices; however, how to design low-cost, high-performance solid electrolytes has become a critical challenge in the energy field, and significant progress has not been achieved until now. Here, lake-water-based semisolid electrolytes with a low cost of 1.89 $ kg-1 have been put forward for the purpose of market promotion. By virtue of the palygorskite dopants and lake water source, the electrolytes display satisfying mechanical, electrical, and electrochemical properties as well as economic benefits. The application potential of electrolytes has been demonstrated by employing a polyelectrolyte with ionic conductivity of 0.82 × 10-4 S cm-1 in flexible supercapacitors. The as-assembled devices give a high energy density of 54.72 Wh kg-1 and excellent cycling stability with a capacity retention of 94.8% over 20 000 cycles. The flexibility of devices has been verified through 5000 repetitive bending tests. Our work presents insight into the design of flexible solid electrolytes based on cheap and green raw materials.

Structural design and fabrication of metal vanadate hydrates for wearable electronic applications

The structural design of electroactive materials including rich profits of high capacitance/capacity and exalted durability is of considerable importance in the development of high-performance wearable energy storage technologies. Herein, a simple and single-step hydrothermal approach is demonstrated to design hierarchical feathers-like microsheet arrays for asymmetric supercapacitors (ASCs) with stable cycling performance. The preparation is carried out at low temperatures without any annealing process, and the as-designed nickel/cobalt vanadate hydrates supported on conductive carbon cloth textile are endowed with the unique architecture of feathers-like microsheets, which allows for the effective contact of active materials, rapid ion diffusion, easy electrolyte penetration, and fast electron transfer. Considering these merits in amalgamation, the Ni0.33Co0.67 vanadate hydrate active material shows a superior areal/specific capacity value of 373.9 µAh cm−2/140 mAh g−1 with outstanding cycling performance (100,000 cycles) than those in the design of mono NiV and CoV hydrates as well as the other fabricated electrode (Ni:Co ratio) materials. Furthermore, the Ni0.33Co0.67 vanadate hydrate active material, when employed as a positive electrode for ASCs, demonstrates excellent electrochemical performance. The assembled ASC exhibits high energy and power density values of 0.19 mWh cm−2 and 2.04 mW cm−2, respectively along with remarkable cycling retention of 82.2% after the completion of 100,000 cycles. Also, the as-assembled device was tested by powering different wearable electronics. This work creates a new pathway for the fabrication of single-step Ni-Co vanadate hydrates for durable electrochemical energy storage applications.

Wide-Temperature-Range Flexible Micro-Supercapacitors Using Liquid Crystal Gel Electrolyte

In this work, to construct a sunlight-powered energy storage system, single wall carbon nanotubes (SWCNTs)-based symmetric micro-supercapacitors (MSCs) were fabricated by a one-step, facile spraying method. The electrodes exhibited satisfactory conductivity with a sheet resistance of 275 Ω/sq. Moreover, potassium hydroxide-poly(vinyl alcohol) (KOH-PVA) and phosphoric acid-nonionic surfactant liquid crystal (PA-NI LC) gel electrolytes were prepared and applied to design all-solid-state MSC devices. Compared to the device assembled using the SWCNTs/KOH-PVA gel electrolyte, the SWCNTs/PA-NI LC electrolyte displayed larger areal capacitance with the largest recorded value of 11.0 mF·cm–2 at a current density of 0.08 mA·cm–2 at room temperature. Additionally, the effect of temperature on the MSC device performance was assessed, and the results revealed that the device based on the SWCNTs/PA-NI LC electrolyte achieved enhanced electrochemical performance at an operating temperature of 65 °C, including a large areal capacitance of 14.7 mF·cm–2 at 0.08 mA·cm–2, a better rate performance of 88% with 12.9 mF·cm–2 at 0.4 mA·cm–2, and a higher energy density of 2.04 μWh·cm–2 at a power density of 40.64 μW·cm–2. In addition, the MSC device featured high cyclic stability under bending conditions (45 or 90°) at room temperature. Furthermore, a sunlight-powered energy storage system was fabricated, combining solar cells with the as-assembled MSC devices. Three MSCs connected in series were charged by solar cells and further acted as the energy supply for a red light-emitting diode (LED), which could be continuously operated for 2 min 30 s. All of the findings herein represent a good indication of the promising practical application potential of the as-prepared MSC devices as energy storage devices at high temperatures.

Minimization of the electrical contact resistance in thin-film thermoelectric device

High electrical contact resistance refrains the performance of thin-film thermoelectric devices at the demonstrative level. Here, an additional Ti contact layer is developed to minimize the electrical contact resistance to ∼4.8 Ω in an as-assembled thin-film device with 50 pairs of p–n junctions. A detailed interface characterization demonstrates that the low electrical contact resistance should be mainly attributed to the partial epitaxial growth of Bi2Te3-based thin-film materials. Correspondingly, the superlow electrical contact resistance facilitates the applicability of the out-of-plane thin-film device and results in an ultrahigh surface output power density of ∼81 μW cm−2 at a low temperature difference of 5 K. This study illustrates the Ti contact layer that strengthens the contact between Cu electrodes and Bi2Te3-based thermoelectric thin films mainly through partial epitaxial growth and contributes to high-performance thin-film thermoelectric devices.

One-step electrodeposited Ni3S2/Co9S8/NiS composite on Ni foam as high-performance electrode for supercapacitors.

Transition metal sulfides (TMSs) are considered as one of the promising electrode materials due to their fascinating redox reversibility and electronic conductivity. However, volume expansion during the charge/discharge process impedes their practical applications. The reasonable design of TMS electrode materials with unique morphology can improve the energy storage performance. Herein, we prepared the Ni3S2/Co9S8/NiS composite that is in situ grown on Ni foam (NF) via a one-step electrodeposition process. The optimized Ni3S2/Co9S8/NiS-7 shows a superhigh specific capacity of 2785.3 F g-1 at 1 A g-1 and remarkable rate capability. Furthermore, the as-assembled device displays a high energy density of 40.1 W h kg-1 at a power density of 799.3 W kg-1 and a satisfactory stability of 96.6% retention after 5000 cycles. This work provides a facile way to fabricate new TMS electrode materials for high-performance supercapacitors.

An aqueous aluminum-ion electrochromic energy storage device with visual energy level

Electrochromic energy storage devices (EESDs) integrate energy storage and electrochromism into one smart device that can realize the visualization of the energy level by the naked eyes, which has attracted extensive attention in recent years. It is critical to explore suitable electrode materials for achieving both high electrochromic and electrochemical performance. Herein, we propose an aqueous aluminum-ion electrochromic energy storage device (AIEESD) by assembling the polyaniline (PANI) electrochromic cathode, Al metal frame anode and AlCl 3 electrolyte, which yields an open-circuit voltage of ∼1.22 V and a fast self-bleaching behavior without any energy input. Additionally, the developed device exhibits outstanding electrochromic energy storage performances with discharging capacity of 68.1 mAh m −2 , excellent rate capability, large optical modulation (ΔT = 55% at 630 nm) and high coloration efficiency (93.62 cm 2 C −1 at 630 nm). Moreover, the prototype device can reversibly switch between the multicolor (transparent, light yellow, green and dark blue) when the voltage changes from 0.4 to 2.5 V, which means the energy status can be monitored by the obvious color transition. These results show that the AIEESD in this work has great application prospects for smart windows and energy storage displays. An aqueous aluminum-ion electrochromic energy storage device based on PANI cathode has been developed, and it demonstrates fast spontaneous bleaching process without any external energy input. The as-assembled device exhibits both high electrochromic and energy storage performances due to the multivalent-ions interaction with PANI materials. Importantly, the device demonstrates its energy level by displaying multi-colors from dark blue, green, light yellow to transparent and shows potential applications in graphic display. • An aqueous aluminum-ion electrochromic energy storage device is developed. • The prototype device can achieve the visualization of the energy status. • The device demonstrates energy retrieve function and multicolor graphical display.

Synthesis and characterization of SrFeOx hetero-film resistance-switching device with low operation voltage

As a critical topological phase transition material, SrFeOx could play an essential role in the field of resistive memory. How to implement resistance-switching more softly and ensure the stability of materials has always been a relevant research hotspot. Regulating the oxygen environment during the deposition process of the films can effectively control the stoichiometry of the functional layer and then improve the resistance-switching characteristics of the device. In this paper, a SrFeOx hetero-film was prepared by oxygen pretreatment on the SrRuO3 surface before SrFeOx deposition, and the as-assembled micrometer-scale device exhibits a low set operating voltage of 0.6 V and favorable cycling characteristics. The SrFeOx hetero-film reveals a vertical brownmillerite superlattice-like structure with ∼20 nm perovskite buffer layer, which benefits the connection and rupture of conductive filament. Additionally, XPS and UV–vis were used to analyze the bonding energy and band gap of SrFeOx hetero-film, and offers the experimental basis for the explanation of the conductive mechanism. Therefore, the device based on SrFeOx hetero-film with low operation voltage provides a reference for low power consumption research on topological phase transition material.

Towards High-Performance Supercapacitor Electrodes via Achieving 3D Cross-Network and Favorable Surface Chemistry.

Transition metal phosphides/phosphates (TMPs) are considered appealing electrode materials in energy-related fields, especially in supercapacitors. However, the dilemma of inadequate electrode kinetics and dimensional unreliability evoked by a huge volume variation during cycling significantly plagues their progress. To mitigate this issue, in this work, a 3D cross-network in situ assembled via self-derived N-doped carbon hybrid Ni-Co-P/POx 2D sheets is fabricated. Particularly, high-Fermi-level N-doped carbon well confines Ni-Co-P/POx nanoparticles at the molecular level, and N-doping leads to redistribution of spin/electron density in the carbon skeleton, effectively regulating the electron environment of nearby Ni-Co-based moieties, resulting in a relatively lower surface work function, as known via experimental and Kelvin probe force microscopy (KPFM) results, which favors electron flee from the electrode surface and facilitates electron transport toward a rapid supercapacitor response. Moreover, the well-defined 3D cross-network architectures featured with in-plane pores and interconnected with each other can provide more ion/electron transfer pathways and 2D sheets with excellent surface chemistry available for sustainable ion/electron mobility, synergistically affording the favorable electrode kinetics. Accordingly, the resultant Ni-Co-P/POx@NC electrode shows admirable specific capacitance, excellent rate survivability, and long-term cyclability. The as-assembled asymmetric device exhibits remarkable energy and power outputs (48.5 Wh kg-1 and 7500 W kg-1), superior to many reported devices. Furthermore, our devices possess the prominent ability to power a commercial electronic thermometer for 1560 s at least, showcasing superb application prospects.

Flexible aqueous asymmetric capacitor with SiC-decorated boron-doped graphene cathode and core–shell SiC@graphene anode

• Core-shell SiC@graphene (Gr) nanoparticles were synthesized as an anode material. • B-doped graphene (BGr) nanosheets embedded with SiC nanoparticles were synthesized. • SiC-BGr electrocatalyzed the NiOOH/NiO redox reaction to improve pseudocapacitance. • SiC-BGr cathode showed the maximum specific capacitance of 1803 mF cm −2 at 4 mA cm −2 . • Aqueous SiC-BGr//SiC@Gr capacitor showed high working voltage and stability. Flexible aqueous pseudocapacitors have the advantages of high specific capacitance, high safety, low cost, and fast ion diffusion. However, the development of such devices is a challenge because of the low stability of the active material and the high interface resistance of the current collector-active material. In this study, we used silicon carbide (SiC)-boron-doped graphene (BGr) nanosheets and core–shell SiC@Gr nanoparticles as the cathode and anode, respectively, and constructed a flexible aqueous asymmetric capacitor (ASC) with a 3 M NaOH/carboxymethyl cellulose hydrogel as the electrolyte. In an aqueous NaOH solution, the optimized SiC-BGr cathode showed a specific capacitance of 1384.3 mF cm −2 (461.4 F g −1 ) at the current density of 3 mA cm −2 (1 A g −1 ), and the core–shell SiC@Gr anode showed a wide potential window of −1.0–0 V. The as-assembled ASC device had a high working voltage of 1.4 V, delivered an excellent capacitance of 337.1 mF cm −2 , and retained 86% of its initial capacitance after 10 000 cycles. Furthermore, the ASC also showed high energy density (57.3 μWh cm −2 ), high power density (6536.9 μW cm −2 ), high bending stability, and applicability at a low temperature of −20 °C. Thus, the preparation of novel SiC-Gr materials can promote the development of flexible aqueous capacitors with high working voltage and good temperature adaptability for application in the field of wearable electronic devices with safety, strong environmental adaptability, and reliable performance.

Natural ore molybdenite as a high-capacity and cheap anode material for advanced lithium-ion capacitors

Hybrid lithium-ion capacitors (LICs) receive special interests because they work by combining the merits of high-capacity lithium-ion batteries and high-rate capacitors in a Li salt containing electrolyte, so as to bridge the gap between the two devices. One of main challenges for LICs is to develop inexpensive and superior anode materials at high rates. In this work, natural molybdenite was utilized as precursor to achieve the scalable production of cheap MoS2/carbon composites. This molybdenite-derived MoS2/carbon electrode can not only exhibit excellent Li+-storage performances including ultrahigh specific capacity (1427 mAh g–1 after 1000 cycles at 1 A g–1) and rate capability (554 mAh g–1 at 10 A g–1), but also possess four-times higher tap density than that of commercial graphite. By employing MoS2/carbon as the anode and activated carbon as the cathode, the as-assembled LIC device delivers both high energy//high power density and long cycle lifespan. Furthermore, the price is nearly 200 orders of magnitude lower than the traditional high-purity chemicals, which can be easily scaled up to achieve high-throughput production.

Synchronous Defect and Interface Engineering of NiMoO4 Nanowire Arrays for High-Performance Supercapacitors.

Developing high-performance electrode materials is in high demand for the development of supercapacitors. Herein, defect and interface engineering has been simultaneously realized in NiMoO4 nanowire arrays (NWAs) using a simple sucrose coating followed by an annealing process. The resultant hierarchical oxygen-deficient NiMoO4@C NWAs (denoted as “NiMoO4−x@C”) are grown directly on conductive ferronickel foam substrates. This composite affords direct electrical contact with the substrates and directional electron transport, as well as short ionic diffusion pathways. Furthermore, the coating of the amorphous carbon shell and the introduction of oxygen vacancies effectively enhance the electrical conductivity of NiMoO4. In addition, the coated carbon layer improves the structural stability of the NiMoO4 in the whole charging and discharging process, significantly enhancing the cycling stability of the electrode. Consequently, the NiMoO4−x@C electrode delivers a high areal capacitance of 2.24 F cm−2 (1720 F g−1) at a current density of 1 mA cm−2 and superior cycling stability of 84.5% retention after 6000 cycles at 20 mA cm−2. Furthermore, an asymmetric super-capacitor device (ASC) has been constructed with NiMoO4−x@C as the positive electrode and activated carbon (AC) as the negative electrode. The as-assembled ASC device shows excellent electrochemical performance with a high energy density of 51.6 W h kg−1 at a power density of 203.95 W kg−1. Moreover, the NiMoO4//AC ASC device manifests remarkable cyclability with 84.5% of capacitance retention over 6000 cycles. The results demonstrate that the NiMoO4−x@C composite is a promising material for electrochemical energy storage. This work can give new insights on the design and development of novel functional electrode materials via defect and interface engineering through simple yet effective chemical routes.

NiCo layered double hydroxide nanosheets with enhanced electrochemical performance

As important electrode materials, 2D layered double hydroxides (LDHs) have attracted much attention owing to their high reaction activity, tunable composition and unique structure. However, the poor cycling stability restricts their large scale industrial applications. To solve this problem, we fabricate several NiCo-LDH nanosheets through regulating the ratio of Ni and Co ions. The as-obtained samples are utilized as cathode for supecapacitor. Thereinto, the NiCo3-LDH product possess a specific capacitance of 699 C g−1 at 1 A g−1. The as-assembled device delivers an energy density of 90.75 W h kg−1 at 2700 W kg−1 and keep 91.84% of its initial capacitance after 10000 cycles. Moreover, as oxygen evolution reaction (OER) electrocatalysts, the obtained product presents an overpotential of 270 mV at 20 mA cm−2 and excellent cycle stability.

Approaching high performance Ni(Co) molybdate electrode materials for flexible hybrid devices.

Transition metal molybdates are widely used as electrode materials for supercapacitors due to their high theoretical specific capacitance and excellent electrochemical activity. It is an effective strategy to improve the electrochemical performance by reasonably designing electrode materials. Herein, we prepared several Ni1-xCoxMoO4·nH2O nanostructures through facile hydrothermal strategies. Benefiting from the synergistic effects between Ni and Co elements, the obtained electrode materials delivered a specific capacitance of 1390 F g−1 at 1 A g−1. The as-assembled device shows an energy density of 72.45 W h kg−1 at a power density of 2688.8 W kg−1. It also presents excellent cycling and mechanical stability after many times of charging and discharging processes and bending.

High-Energy Density Aqueous Zinc–Iodine Batteries with Ultra-long Cycle Life Enabled by the ZnI2 Additive

Aqueous zinc–iodine batteries, featuring high energy density, safety, and cost-effectiveness, have been regarded as a promising energy storage system. Nevertheless, poor cycling stability and dissolution of iodine/polyiodide have greatly limited the development of zinc–iodine batteries. Here, iodine encapsulated by hierarchical porous carbon is employed as a positive material to assemble high-performance zinc–iodine batteries. Meanwhile, the utilization of the ZnI2 additive in the electrolyte can enhance the capacity and cycling stability of as-assembled devices because the existence of polyiodide (I3– and I5–) can effectively inhibit the dissolution of iodine. Thanks to the high conductivity and interconnected structure of the prepared carbon material, the as-assembled zinc–iodine batteries deliver an excellent specific capacity of 360.6 mA h g–1 at 0.5 C, a superb durability (∼98.4% retention of the initial capacity at a high density of 50 C after 35,000 cycles), and an ultra-high energy/power density of 422.6 W h kg–1/21.6 kW kg–1. Significantly, the mechanism of the constructed device was investigated by ex-situ Raman and ex-situ X-ray diffraction. Besides, when coupling carbon@I2 electrodes with the hydrogel electrolyte to assemble quasi-solid-state zinc–iodine batteries, the as-built device can well service for an electronic clock.

Alkaline aqueous rechargeable Ni-Fe batteries with high-performance based on flower-like hierarchical NiCo2O4 microspheres and vines-grapes-like Fe3O4-NGC composites

Aqueous rechargeable secondary Ni-Fe batteries have attracted extensive attention due to low cost, relatively outstanding safety and high energy density. However, the nickel/iron electrode materials also suffer from poor conductivity and week cycling performance. In this study, we have modified the CNT-S-PEGm as electron transport channels with methoxypolyethylene glycol (mPEG) via thiol-ene click to further provide more reactive sites, and then prepared the cathode materials of 3D flower-like hierarchical microspheres of NiCo2O4-CNT-S-PEGm composites by a solvothermal method. The as-prepared cathode materials reveal the capacity of 195.7 mAh g−1 at 0.5 A g−1. In addition, the anode materials of vines-grapes-like Fe3O4-N-rGO-CNT>N-PEGm (Fe3O4-NGC) ternary composites have been prepared in a typical hydrothermal method. Notably, the promising Fe3O4-NGC anode materials exhibit the highest capacity of 308.1 mAh g−1 at 1 A g−1. Due to such excellent attributes, the alkaline aqueous rechargeable Ni-Fe batteries of NiCo2O4-CNT-S-PEGm//Fe3O4-NGC have been successfully fabricated. Moreover, the as-assembled device displays the high capacity of 77.8 mAh g−1 at 0.5 A g−1 and the energy density of 64.4 Wh kg−1 at 414 W kg−1 for potential energy storage.

One-step synthesis of hierarchical Ni3Se2 nanosheet-on-nanorods/Ni foam electrodes for hybrid supercapacitors

Transitional metal selenides have high conductivity, even metal quality, which makes them great for using as electrode materials for fabricating supercapacitors. Here, hierarchical Ni3Se2 nanosheet-on-nanorods on Ni foam (NSR-Ni3Se2/Ni) was fabricated by a facile three-dimensional (3D) substrate-assisted confinement assembly method, and used as a freestanding electrode material for hybrid supercapacitors (HSCs). In this design, metallic Ni3Se2 with hybrid 1D/2D architecture could effectively enhance the active specific surface area of electrode and improve space utilization, as well as significantly facilitate electrons transport, while Ni foam served as the Ni source of Ni3Se2 and provided 3D multi-electron transport channels, thus boosting the specific capacity. The constructed hierarchical NSR-Ni3Se2 electrode delivered a superior areal specific capacity of 1.068 mAh/cm2 (7.69 F/cm2) at 2 mA/cm2 and retained 68.2% of the initial capacity when the current density increases by 15 times. Furthermore, the as-assembled NSR-Ni3Se2 device exhibited an ultrahigh energy density of 56.4 Wh/kg and high power density of 4640.3 W/kg, and a capacity retention of 92.6% even after 6000 cycles.