Qiufan Wang

Flexible Asymmetric Supercapacitors Based upon Co9S8 Nanorod//Co3O4@RuO2 Nanosheet Arrays on Carbon Cloth

We have successfully fabricated flexible asymmetric supercapacitors (ASCs) based on acicular Co9S8 nanorod arrays as positive materials and Co3O4@RuO2 nanosheet arrays as negative materials on woven carbon fabrics. Co9S8 nanorod arrays were synthesized by a hydrothermal sulfuration treatment of acicular Co3O4 nanorod arrays, while the RuO2 was directly deposited on the Co3O4 nanorod arrays. Carbon cloth was selected as both the substrate and the current collector for its good conductivity, high flexibility, good physical strength, and lightweight architecture. Both aqueous KOH solutions and polyvinyl alcohol (PVA)/KOH were employed as electrolyte for electrochemical measurements. The as-fabricated ASCs can be cycled reversibly in the range of 0-1.6 V and exhibit superior electrochemical performance with an energy density of 1.21 mWh/cm(3) at a power density of 13.29 W/cm(3) in aqueous electrolyte and an energy density of 1.44 mWh/cm(3) at the power density of 0.89 W/cm(3) in solid-state electrolyte, which are almost 10-fold higher than those reported in early ASC work. Moreover, they present excellent cycling performance at multirate currents and large currents after thousands of cycles. The high-performance nanostructured ASCs have significant potential applications in portable electronics and electrical vehicles.

Fiber‐Based Flexible All‐Solid‐State Asymmetric Supercapacitors for Integrated Photodetecting System

Integrated nanodevices with the capability of storing energy are widely applicable and have thus been studied extensively. To meet the demand for flexible integrated devices, all-solid-state asymmetric supercapacitors that simultaneously realize energy storage and optoelectronic detection were fabricated by growing Co3 O4 nanowires on nickel fibers, thus giving the positive electrode, and employing graphene as both the negative electrode and light-sensitive material. The as-assembled integrated systems were characterized by an improved energy storage, enhanced power density (at least by 1860 % enhanced) by improving the potential window from 0-0.6 V to 0-1.5 V, excellent photoresponse to white light, and superior flexibility of both the fiber-based asymmetric supercapacitor and the photodetector. Such flexible integrated devices might be used in smart and self-powered sensory, wearable, and portable electronics.

Morphology evolution of urchin-like NiCo2O4 nanostructures and their applications as psuedocapacitors and photoelectrochemical cells

Urchin-like NiCo2O4 nanostructures were synthesized on a large scale via a simple hydrothermal method free of any template and catalyst. As-synthesized NiCo2O4 urchins have uniform diameters of 5 μm with numerous small nanorods radially grown from the center. Typical nanorods have diameters of 100–200 nm and lengths of about 2 μm. Studies found that urea plays an important role to determine the morphology of the products and a “rods-to-straw-bundles-to-urchins” mechanism was proposed. With a porous structure and a large surface area of 99.3 m2 g−1, the prepared NiCo2O4 urchins exhibited superior specific capacitance of 1650 and 1348 F g−1 at current densities of 1 and 15 A g−1, respectively. The capacitance loss after 2000 cycles is only 9.2% at the current density of 8 A g−1, indicating their excellent cycling stability. Photoelectrochemical cells were also fabricated on the urchin-like NiCo2O4 nanostructures with the features of fast photocurrent response and excellent stability. A high photocurrent response of about 70 μA cm−2 was observed.

NiCo2O4 nanowire arrays supported on Ni foam for high-performance flexible all-solid-state supercapacitors

Portable electronic devices which are ultrathin, lightweight and even able to roll-up have attracted much attention. Herein, we report the design of flexible all-solid-state symmetric supercapacitors by using two NiCo2O4 nanowire arrays supported on Ni foams as the electrodes. The as-fabricated symmetric supercapacitors have excellent electrochemical performance with a high cell areal capacitance of 161 mF cm−2 at 1 mA cm−2. Good electrochemical performance stability over 3000 cycles was obtained even when the device was under harsh mechanical conditions including both twisted and bent states. As-fabricated all-solid-state supercapacitors could be charged and power a commercial light-emitting-diode, demonstrating their feasibility as an efficient energy storage component and self-powered micro/nano-system. In addition, we were able to grow NiCo2O4 nanowire arrays on many kinds of flexible substrates, including nickel foam, carbon cloth, Ti foil and polytetrafluoroethylene tape. Our work here opens up opportunities for the device configuration for energy-storage devices in the future wearable electronic area and many other flexible, lightweight and high performance functional nanoscale devices.

New Energy Storage Option: Toward ZnCo2O4 Nanorods/Nickel Foam Architectures for High-Performance Supercapacitors

Hierarchical ZnCo2O4/nickel foam architectures were first fabricated from a simple scalable solution approach, exhibiting outstanding electrochemical performance in supercapacitors with high specific capacitance (∼1400 F g(-1) at 1 A g(-1)), excellent rate capability (72.5% capacity retention at 20 A g(-1)), and good cycling stability (only 3% loss after 1000 cycles at 6 A g(-1)). All-solid-state supercapacitors were also fabricated by assembling two pieces of the ZnCo2O4-based electrodes, showing superior performance in terms of high specific capacitance and long cycling stability. Our work confirms that the as-prepared architectures can not only be applied in high energy density fields, but also be used in high power density applications, such as electric vehicles, flexible electronics, and energy storage devices.

Three‐Dimensional Hierarchical GeSe2 Nanostructures for High Performance Flexible All‐Solid‐State Supercapacitors

Highly flexible stacked and in-plane all-solid-state supercapacitors are fabricated on 3D hierarchical GeSe2 nanostructures with high performance, and, when configured as a self-powered photodetector nanosystem, can be used to power CdSe nanowire photodetectors.

Ternary oxide nanostructured materials for supercapacitors: a review

Materials engineering plays a key role in the field of electrochemical energy storage, and considerable efforts have been made in recent years to fulfil the future requirements of electrochemical energy storage using novel functional electrode materials. Among the transition metal oxides, ternary metal oxides possess multiple oxidation states that enable multiple redox reactions. They have been reported to exhibit a higher supercapacitive performance than single component metal oxides, and seem to be a group of the most promising and low cost materials for pseudo-capacitors. This paper presents a state-of-the-art review on the research progress of developing ternary oxide nanostructures for supercapacitors, with the focus on the synthesis of one-dimensional (1-D), two-dimensional (2-D) and three-dimensional (3-D) nanostructures and their potential applications in energy storage devices. The remaining challenges toward the rational design of ternary oxide nanostructured electrodes for next-generation supercapacitors are also proposed.

Advanced rechargeable lithium-ion batteries based on bendable ZnCo2O4-urchins-on-carbon-fibers electrodes

AbstractA novel class of ZnCo2O4-urchins-on-carbon-fibers matrix has been designed, characterized, and used to fabricate high-performance energy storage devices. We obtained a reversible lithium storage capacity of 1180 mA·h/g even after 100 cycles, demonstrating the highreversible capacity and excellent cycle life of the as-prepared samples. Tested as fast-charging batteries, these electrodes exhibited a considerable capacity of 750 mA·h/g at an exceptionally high rate of 20 C (18 A/g), with an excellent cycle life (as long as 100 cycles), which are the best high-rate results reported at such a high charge/discharge current density for ZnCo2O4-based anode materials in lithium rechargeable batteries. Such attractive properties may be attributed to the unique structure of the binder-free ZnCo2O4-urchins-on-carbon-fibers matrix. Full batteries were also developed by combining the ZnCo2O4 anodes with commercial LiCoO2 cathodes, which showed flexible/wearable and stable features for use as very promising future energy storage units.

Ultralong-life and high-rate web-like Li4Ti5O12 anode for high-performance flexible lithium-ion batteries

Flexible lithium ion batteries (LIBs) have recently attracted increasing attention as they show unique promising advantages, such as flexibility, shape diversity, and light weight. Similar to conventional LIBs, flexible LIBs with long cycle life and high-rate performance are very important for applications of high performance flexible electronics. Herein, we report a three-dimensional (3D) web-like binderfree Li4Ti5O12 (LTO) anode assembled from numerous 1D nanowires exhibiting excellent cycling performance with high capacities of 153 and 115 mA·h·g−1 after 5,000 cycles at 2 C and 20 C, respectively, and excellent rate property with a capacity of 103 mA·h·g−1 even at a very high current rate of 80 C. Surprisingly, a flexible full battery assembled from the web-like LTO nanostructure and LiMn2O4 (LMO) nanorods exhibited a high capacity of 125 mA·h·g−1 at high current rate of 20 C, and showed excellent flexibility with little performance degradation even in seriously bent states.

Efficient synthesis of hierarchical NiO nanosheets for high-performance flexible all-solid-state supercapacitors

Hierarchical NiO nanosheets were successfully grown on flexible carbon fibers with pre-deposited ZnO nanoparticle films as the buffer layers, followed by the removal of the ZnO films. The as-grown NiO nanosheets with excellent flexibility exhibited a largest specific capacitance of 842 mF cm−2 at a current density of 1 mA cm−2. Configured as flexible symmetric all-solid-state supercapacitors, the device showed a specific capacitance of 20 mF cm−2 at 0.1 mA cm−2, excellent cyclability with a real capacitance of about 20 mF cm−2 for over 10000 cycles, and excellent mechanical flexibility and stability under different curvatures.