High-performance and flexible all-solid-state hybrid supercapacitor constructed by NiCoP/CNT and N-doped carbon coated CNT nanoarrays

High-performance VO2/CNT@PANI with core-shell construction enable printable in-planar symmetric supercapacitors

As a progressive electronic energy storage device, the flexible supercapacitor holds tremendous promise for powering wearable/portable electronic products. Of various pseudocapacitor materials, vanadium dioxide (VO2) has garnered extensive attention due to its impressive theoretical capacitance. However, the challenges of inferior cycling life and lower energy density to be addressed. Herein, we prepare VO2 nanorods with winding carbon nanotubes (CNT) via a facile solvothermal route, followed by in situ polymerization of polyaniline (PANI) shell. Taking full advantage of the synergistic effect, the VO2/CNT@PANI composite delivers a high specific capacitance of 354.2F/g at 0.5 A/g and a long cycling life of ∼ 88.2 % over 5000 cycles resulting from the enhanced conductivity of CNT and stabilization of PANI shell. By screen printing the formulated inks with outstanding rheological behaviours, we manufacture an in-planar VO2/CNT@PANI symmetric supercapacitor (VO2/CNT@PANI SSC) device featuring an orderly arrangement structure. This device yields a remarkable areal energy density of 99.57 μWh/cm2 at a power density of 387.5 μW/cm2 while retaining approximately ∼ 87.6 % of its initial capacitance after prolonged use. Furthermore, we successfully powered a portable game machine for more than 2 min using two SSCs connected in series with ease. Therefore, this work presents a universal strategy that utilises combination and coating to boost electrochemical performance for flexible high-performance supercapacitors.

Construction and application of NiCo2O4@MnS composite with hierarchical structure for hybrid supercapacitor

The development of an electrochemical energy storage system with exceptional performance is an important way to address the energy crisis and environmental pollution of the modem world. In this study, an NiCo2O4@MnS composite with a unique hierarchical structure has been successfully synthesized on an NF substrate using the hydrothermal-electrodeposition method. The results indicate that NiCo2O4@MnS possesses superior specific capacitance and excellent cycling stability. At a current density of 2 A g-1, its specific capacitance can reach 2100 F g-1, while the capacitance retention is still 76% after 10 000 cycles at 10 A g-1. Moreover, when the current density is 1 A g-1, the assembled NiCo2O4@MnS//AC device can deliver a specific capacitance of 203 F g-1, and the energy density is up to 55 W h kg-1 at a power density of 697 W kg-1. These outstanding electrochemical properties of NiCo2O4@MnS can be ascribed to the increase in ion diffusion, specific surface area and electronic conductivity due to its unique hierarchical structure and introduction of MnS.

Achieving stable Zn metal anode via a hydrophobic and Zn2+-conductive amorphous carbon interface

High security and low cost enable aqueous zinc ion batteries (AZIBs) with huge application potential in large-scale energy storage. Nevertheless, the loathsome dendrite and side reactions of Zn anode are harmful to the cycling lifespan of AZIBs. Here, a new type of thin amorphous carbon (AC) interface layer (∼100 nm in thickness) is in-situ constructed on the Zn foil (Zn@AC) via a facile low-temperature chemical vapor deposition (LTCVD) method, which owns a hydrophobic peculiarity and a high Zn2+ transference rate. Moreover, this AC coating can homogenize the surface electric field and Zn2+ flux to realize the uniform deposition of Zn. Consequently, dendrite growth and side reactions are concurrently mitigated. Symmetrical cell achieves a dendrite-free Zn plating/stripping over 500 h with a low overpotential of 31 mV at 1 mA cm-2/1 mAh cm-2. Of note, the full cell with a MnO2/CNT cathode harvests a capacity retention of 70.0 % after 550 cycles at 1 A/g. In addition, the assembled flexible quasi-solid-state AZIBs display a stable electrochemical performance under deformation conditions and maintain a capacity of 76.5 mAh/g at 5 A/g after 300 cycles. This innovative amorphous carbon layer is expected to provide a new insight into stabilizing Zn anode.

A bimetallic Fe-Mg MOF with a dual role as an electrode in asymmetric supercapacitors and an efficient electrocatalyst for hydrogen evolution reaction (HER)

In this work, a novel bimetallic Fe-Mg/MOF was synthesized through a cost-effective and rapid hydrothermal process. The structure, morphology, and composition were examined using X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy. Further, the Brunauer-Emmett-Teller (BET) measurement showed a 324 m2 g-1 surface area for Fe-Mg/MOF. The Fe-Mg/MOF achieved 1825 C g-1 capacity at 1.2 A g-1 current density, which is higher than simple Fe-MOF (1144 C g-1) and Mg-MOF (1401 C g-1). To assess the long-term stability of the asymmetric device, the bimetallic MOF supercapattery underwent 1000 charge/discharge cycles and retained 85% of its initial capacity. The energy and power densities were calculated to be 57 W h kg-1 and 2393 W kg-1, respectively. Additionally, Fe-Mg/MOF showed superior electrocatalytic performance in hydrogen evolution reaction (HER) by demonstrating a smaller Tafel slope of 51.43 mV dec-1. Our research lays the foundation for enhancing the efficiency of energy storage technologies, paving the way for more sustainable and robust energy solutions.

Heterostructured Ni3B/Ni nanosheets for excellent microwave absorption and supercapacitive application

The development of electronic information technology has placed higher demands on microwave absorption materials (MAMs), especially the exploration of novel MAMs to broaden their application. At present, little attention has been given the wave absorption properties of transition metal borides (TMBs). In this work, a simple and economical method is developed to prepare Ni₃B/Ni heterostructure nanosheets and their possible applications for microwave absorption (MA) and supercapacitor are evaluated. It is worth noting that Ni₃B/Ni nanosheets exhibit excellent MA properties due to the aggregated nanosheet-like morphology of Ni₃B/Ni with enhancing interfacial polarization, as well as the synergistic effect of dielectric and magnetic losses. It is observed in experiments that the minimum reflection loss value of Ni₃B/Ni is -41.60 dB at 16.8 GHz. Moreover, the maximum effective absorption bandwidth can reach 3.28 GHz. Furthermore, Ni₃B/Ni has good energy storage characteristics and is able to provide a specific capacity of 1150.6F g^-1 at a current density of 1 A g^-1. Meanwhile, it has the ability to maintain an initial capacity of 74.4 % after 1000 cycles at a current density of 10 A g^-1. Therefore, this study provides an idea to explore TMBs as high-performance MA and supercapacitor materials.

High-performance flexible supercapacitor enabled by Polypyrrole-coated NiCoP@CNT electrode for wearable devices

As a pseudocapacitive electrode material, nickel-cobalt bimetallic phosphide has attracted wide attention with its advantage in capacitance and chemical activity. While, like Ni-Co oxides or sulfides, the application of nickel-cobalt bimetallic phosphide is generally hampered by its confined conductivity, low chemical stability and unsatisfactory cycle durability. Herein, this work demonstrates a NiCoP@CNT@PPy (NCP@CNT@PPy) composite that is obtained by polymerizing pyrrole monomer on the surface of NiCoP@CNT complex. According to density functional theory (DFT), it is theoretically demonstrated that the bimetallic Ni-Co phosphide (NiCoP) can exhibit more electrons near the Fermi level than single Ni or Co phosphide. Under the combined effects of carboxylic carbon nanotubes (c-CNTs) and polypyrrole (PPy), the NCP@CNT@PPy electrode exhibits excellent electrochemical performance. In addition, a flexible asymmetric supercapacitor (ASC) is prepared, which demonstrated high energy density and admirable heat-resistance and flexibility performance, showing huge potential in the application of heat-resistant storage energy systems and portable wearable devices.

Sonochemically exfoliated polymer-carbon nanotube interface for high performance supercapacitors

Energy storage characteristics of organic molecules continue to attract attention for supercapacitor applications, as they offer simple processing and can be employed for flexible devices. The current study utilized the ultrasonically driven exfoliation to obtain poly diketo pyrrolopyrrole-thieno thiophene (PDPT) and multiwalled carbon nanotube (CNT) composite, subsequently fabricated a PDPT donor-π-acceptor heterojunction with CNT and investigated energy storage applications. The composite was characterized using series of standard analytical techniques. Morphology indicated well alighted CNT tubes on PDPT polymer nanosheets with an effective interface, providing efficient electrochemical regions, enabling fast charge transfer between PDPT and CNT. We also investigated the PDPT-CNT composite electrochemical behavior, achieving 319.2 and 105.7F.g^-1 capacitances for PDPT-CNT and PDPT at 0.5 A.g^-1 current density for three electrode configurations; and 126 and 42F.g^-1 for symmetric structures, respectively. Experimental results confirmed that PDPT-CNT composite electrodes achieved two fold the capacitance compared with PDPT alone. The hypothesis and synthetic approach provide an excellent candidate for conjugated polymers with carbon nanotubes and energy related devices.

High-performance supercapacitor based on highly active P-doped one-dimension/two-dimension hierarchical NiCo2O4/NiMoO4 for efficient energy storage

Multi-dimensional metal oxides have become a promising alternative electrode material for supercapacitors due to their inherent large surface area. Herein, P-doped NiCo₂O₄/NiMoO₄ multi-dimensional nanostructures are synthesized on carbon clothes (CC) with a continuous multistep strategy. Especially, P has the best synergistic effect with transition metals, such as optimal deprotonation energy and OH^- adsorption energy, which can further enhance electrochemical reaction activity. For the above reasons, the P-NiCo₂O₄/NiMoO₄@CC electrode exhibits an ultra-high specific capacitance of 2334.0 F g^-1 at 1 A g^-1. After 1500 cycles at a current density of 10 A g^-1, its specific capacity still maintains 93.7%. Besides, a P-NiCo₂O₄/NiMoO₄@CC//activated carbon device (hybrid supercapacitor or device) was also prepared with a maximum energy density of 45.1 Wh kg^-1 at a power density of 800 W kg^-1. In particular, the capacity retention rate is still 89.97% after 8000 cycles due to its excellent structural stability. Our work demonstrates the vast potential of multi-dimensional metal oxides in energy storage.

Electrochemical performance of the homologous molybdenum(vi) redox-active gel polymer electrolyte system

PVA–H₃PO₄–Na₂MoO₄ and PVA–H₃PO₄–PMo₁₂ are assembled into a single solid-state supercapacitor to improve the specific capacitance. Homologous molybdenum (vi) of PMo₁₂ and Na₂MoO₄ provides synergistic effect to improve faradaic capacitance performance.

Electrospun carbon nanofibers embedded with MOF-derived N-doped porous carbon and ZnO quantum dots for asymmetric flexible supercapacitors

Hierarchical carbon nanofibers are embedded with MOF-derived N-doped porous carbon nanoparticles and decorated with ZnO quantum dots via a co-spinning method.

Titanium niobate (Ti2Nb10O29) anchored on nitrogen-doped carbon foams as flexible and self-supported anode for high-performance lithium ion batteries

Assembling active materials on flexible conductive matrixes for fabricating high-rate, self-supported and durable anodes is essential for the development of high-power flexible lithium-ion batteries. In this study, we report an efficient combinational strategy for producing hybrid composites (TNO@MCF) of Ti₂Nb₁₀O₂₉ (TNO) anchored on melamine carbon foam (MCF) via a hydrothermal method. The N-doped MCF not only showed good electronic conductivity and flexibility, but also improved the ion transport performance of the composites. The TNO@MCF electrode exhibited remarkably high rate capacities (327 mA h g^-1 at 1 C, and 205 mA h g^-1 at 40 C) and excellent cycling stability with a high capacity retention of 81.4% after 1000 cycles at 10 C. After 100 compression-rebound cycles, the TNO@MCF electrode showed a reversible capacity of 315 mA h g^-1 at 1 C and exhibited a capacity retention of 72.3% for 1000 cycles at 10 C. This compressible structure design could provide guidelines for manufacture of other flexible electrodes for energy storage devices.

Hollandite-type β-FeOOH(Cl) as a new cathode material for chloride ion batteries

β-FeOOH is utilized as a new cathode material for rechargeable chloride ion batteries for the first time. β-FeOOH has superior rate capabilities and a high reversible capacity of 122 mA h g^-1 after 100 cycles. This work opens up new possibilities for the development of anion batteries.

Latest Advances in Flexible Symmetric Supercapacitors: From Material Engineering to Wearable Applications

Flexible symmetric supercapacitors (FSSs) have received enormous attention in energy storage and conversion areas by virtue of their superior flexibility, high power density, and good cycling stability. FSS devices are typically composed of one solid electrolyte layer laminated by two electrode layers, which can realize energy storage, response to electrical stimulus, and even detect external stress or strain change based on various working mechanisms. The as-mentioned multifunctions of FSS devices are expected to play many critical roles in practical applications of wearable power supply and in artificial intelligence. This realization strongly associates with the rapid development of materials science and engineering, especially nanomaterials and smart structure design, and the multifunctions are results of rational designs of critical materials, optimization of device dimensions, and selectivity of active ion species.This Account showcases the latest advances in FSS devices concerning several critical aspects from fundamental material engineering to practical wearable applications. We first describe advanced functional materials utilized in flexible solid electrolytes and electrodes of FSS systems. Several highly ion-conductive hydrogel and ionogel electrolytes with excellent mechanical properties have been designed for the fast and stable ionic migration kinetics in devices. Some high-performance electrode materials with high charge storage capacity, efficient electromechanical conversion, and sensitive ionic response are presented for realizing multifunctions of FSS devices. After that, analysis of interfaces in devices on their performances is provided, and the construction strategies of robust interface are displayed as well. We then summarize flexible and wearable applications of FSS devices, including high-energy density power sources, flexible and electroactive actuators, and wearable and sensitive sensors. These multifunctions are realized by optimization of device dimensions, control of ion migration kinetics, and development of advanced materials, and the corresponding working mechanisms of the devices are presented in detail. The long-term development and future research directions of FSS devices are also envisioned.At present, the rise of nanomaterials and nanoscience is providing great opportunity to further improve performances of FSS devices and finally realize their wearable applications. These wearable FSS devices with smart multifunctions will significantly promote the development of next-generation flexible electronics for artificial intelligence. It is expected that this Account can promote tremendous efforts toward fundamental clarification of FSS devices, and the design mentality will accelerate the development of other flexible and wearable electrochemical energy devices.