Nishuang Liu

Solid-State High Performance Flexible Supercapacitors Based on Polypyrrole-MnO2-Carbon Fiber Hybrid Structure

A solid-state flexible supercapacitor (SC) based on organic-inorganic composite structure was fabricated through an “in situ growth for conductive wrapping” and an electrode material of polypyrrole (PPy)-MnO2 nanoflakes-carbon fiber (CF) hybrid structure was obtained. The conductive organic material of PPy greatly improved the electrochemical performance of the device. With a high specific capacitance of 69.3 F cm−3 at a discharge current density of 0.1 A cm−3 and an energy density of 6.16 × 10−3 Wh cm−3 at a power density of 0.04 W cm−3, the device can drive a commercial liquid crystal display (LCD) after being charged. The organic-inorganic composite active materials have enormous potential in energy management and the “in situ growth for conductive wrapping” method might be generalized to open up new strategies for designing next-generation energy storage devices.

Cable-type supercapacitors of three-dimensional cotton thread based multi-grade nanostructures for wearable energy storage.

A novel cable-type flexible supercapacitor with excellent performance is fabricated using 3D polypyrrole(PPy)-MnO2 -CNT-cotton thread multi-grade nanostructure-based electrodes. The multiple supercapacitors with a high areal capacitance 1.49 F cm(-2) at a scan rate of 1 mV s(-1) connected in series and in parallel can successfully drive a LED segment display. Such an excellent performance is attributed to the cumulative effect of conducting single-walled carbon nanotubes on cotton thread, active mesoporous flower-like MnO2 nanoplates, and PPy conductive wrapping layer improving the conductivity, and acting as pseudocapacitance material simultaneously.

Highly Stretchable and Self-Healable Supercapacitor with Reduced Graphene Oxide Based Fiber Springs

In large-scale applications of portable and wearable electronic devices, high-performance supercapacitors are important energy supply sources. However, since the reliability and stability of supercapacitors are generally destroyed by mechanical deformation and damage during practical applications, the stretchability and self-healability must be exploited for the supercapacitors. Preparing the highly stretchable and self-healable electrodes is still a challenge. Here, we report reduced graphene oxide fiber based springs as electrodes for stretchable and self-healable supercapacitors. The fiber springs (diameters of 295 μm) are thick enough to reconnect the broken electrodes accurately by visual inspection. By wrapping fiber springs with a self-healing polymer outer shell, a stretchable and self-healable supercapacitor is successfully realized. The supercapacitor has 82.4% capacitance retention after a large stretch (100%), and 54.2% capacitance retention after the third healing. This work gave an essential strategy for designing and fabricating stretchable and self-healable supercapacitors in next-generation multifunctional electronic devices.

A wire-shaped flexible asymmetric supercapacitor based on carbon fiber coated with a metal oxide and a polymer

Due to high capacitance resulting from the redox character of the MnO2–PPy–carbon and V2O5–PANI–carbon fiber composites, a flexible wire-shaped fiber asymmetric supercapacitor (WFASC) was fabricated using these materials as the positive and negative electrodes, respectively. Especially, the large work function difference between MnO2 and V2O5 help the device to exhibit a wide potential window of 2.0 V and a high areal capacitance of 0.613 F cm−2. As a result, the WFASC showed a maximum energy density of 0.340 mW h cm−2 at a power density of 1.5 mW cm−2 and a maximum power density of 30 mW cm−2 at an energy density of 0.294 mW h cm−2. Furthermore, the device exhibited a perfect stability after 5000 cycles at a current density of 30 mA cm−2, meanwhile, it could withstand the bending test and drive a LED under bending states. All of the above results prove the potential application of WFASC devices.

Electrospun PEDOT:PSS–PVA nanofiber based ultrahigh-strain sensors with controllable electrical conductivity

A novel strain sensor based on poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate)–polyvinyl alcohol (PEDOT:PSS–PVA) nanofibers has been fabricated on Kapton substrate by electrospinning, and fully packaged by encapsulating with a polydimethylsioxane layer. Via controlling the concentration of the additive dimethylsulfoxide, the electrical conductivity of the as-spun PEDOT:PSS–PVA nanofiber network can be tuned over a wide rang from 4.8 × 10−8 to 1.7 × 10−5 S cm−1. This kind of strain sensor has excellent stability, fast response, and a high gauge factor of up to about 396. In the meantime, the device could be driven by solar cells, and could detect tiny and quick human actions, for example bending of a finger.

Field emission from carbon nanotube bundle arrays grown on self-aligned ZnO nanorods

The field emission (FE) properties of carbon nanotube (CNT) bundle arrays grown on vertically self-aligned ZnO nanorods (ZNRs) are reported. The ZNRs were first synthesized on ZnO-seed-coated Si substrate by the vapour phase transport method, and then the radically grown CNTs were grown directly on the surface of the ZNRs from ethanol flames. The CNT/ZNR composite showed a turn-on field of 1.5?V??m?1 (at 0.1??A?cm?2), a threshold field of 4.5?V??m?1 (at 1?mA?cm?2) and a stable emission current with fluctuations of 5%, demonstrating significantly enhanced FE of ZNRs due to the low work function and high aspect ratio of the CNTs, and large surface-to-volume ratio of the underlying ZNRs.

Inkjet printing of conductive patterns and supercapacitors using a multi-walled carbon nanotube/Ag nanoparticle based ink

A multi-walled carbon nanotube (MWCNT) and silver (Ag) nanoparticle ink for inkjet printing was prepared by dispersing MWCNTs and Ag nanoparticles in water with the assistance of sodium dodecylbenzenesulfonate (SDBS). Highly conductive patterns of Ag–MWCNTs were printed on paper using a HP Deskjet 1010 inkjet printer. The patterns showed good stability during the bending test and a low sheet resistance of ∼300 Ω sq−1 after being printed 50 times. By simply adding manganese dioxide (MnO2) nanoparticles with a diameter of 60–90 nm into the ink solution, patterned positive electrodes were prepared for asymmetric supercapacitors (ASCs) with filtrated MWCNT negative electrodes. The ASCs exhibit a wide operating potential window of 1.8 V and excellent electrochemical performances, e.g. a high energy density of 1.28 mW h cm−3 at a power density of 96 mW cm−3 and a high retention ratio of ∼96.9% of its initial capacitance after 3000 cycles. The inkjet-printing acting as a simple, low-cost, non-contact deposition method can be fully integrated with the fabrication process in current printed electronic devices and has potential applications in energy storage.

Ultrathin and Lightweight 3D Free-Standing Ni@NiO Nanowire Membrane Electrode for a Supercapacitor with Excellent Capacitance Retention at High Rates

A free-standing binder-free 3D Ni@NiO nanowire membrane is fabricated by a simple filtration method followed by thermal annealing. With an appropriate annealing temperature, the functional nanowires can keep their rough and echinate surface, and the conductive network composed of welded nickel nanowire cores is well-preserved without isolation (0.53 Ω/sq). The unique 3D multigrade mesporous structure not only accelerates the intercalation and deintercalation velocity of electrolyte ions but also provides numerous electroactive sites for the Faraday reaction. As a result, the supercapacitor electrode can preserve a capacitance retention of 96.1% (36.9 F/cm(3)) with a high discharge current density, indicating its wonderful rate capability. The fabricated membrane electrode exhibits high volumetric capacitance, stable cycling life, and remarkable retention of the capacitance at high rate, energy, and power density, making it a promising candidate for application in portable electronic products.

A Flexible Integrated System Containing a Microsupercapacitor, a Photodetector, and a Wireless Charging Coil

Nowadays, the integrated systems on a plane substrate containing energy harvesting, energy storing, and working units are strongly desired with the fast development of wearable and portable devices. Here, a simple, low cost, and scalable strategy involving ink printing and electrochemical deposition is proposed to fabricate a flexible integrated system on a plane substrate containing an all-solid-state asymmetric microsupercapacitor (MSC), a photoconduct-type photodetector of perovskite nanowires (NWs), and a wireless charging coil. In the asymmetric MSCs, MnO2-PPy and V2O5-PANI composites are used as positive and negative electrodes, respectively. Typical values of energy density in the range of 15-20 mWh cm-3 at power densities of 0.3-2.5 W cm-3 with an operation potential window of 1.6 V are achieved. In the system, the wireless charging coil receives energy from a wireless power transmitter, which then can be stored in the MSC to drive the photoconductive detector of perovskite NWs in sequence. The designed integrated system exhibits a stable photocurrent response comparable with the detector driven by an external power source. This research provides an important routine to fabricate integrated systems.

High optical switching speed and flexible electrochromic display based on WO3 nanoparticles with ZnO nanorod arrays' supported electrode

The electrochromic (EC) property of WO(3) nanoparticles grown on vertically self-aligned ZnO nanorods (ZNRs) is reported. An electrochromic character display based on WO(3) nanoparticle-modified ZnO nanorod arrays on a flexible substrate has been fabricated and demonstrated. The ZNRs were first synthesized on ZnO-seed-coated In(2)O(3):Sn (ITO) glass (1 cm(2) cell) and polyethylene terephthalate (PET) (4 cm(2) cell) substrates by a low temperature hydrothermal method, and then amorphous WO(3) nanoparticles were grown directly on the surface of the ZNRs by the pulsed laser deposition (PLD) method. The ZNR-based EC device shows high transparence, good electrochromic stability and fast switching speed (4.2 and 4 s for coloration and bleaching, respectively, for a 1 cm(2) cell). The good performance of the ZNR electrode-based EC display can be attributed to the large surface area, high crystallinity and good electron transport properties of the ZNR arrays. Its high contrast, fast switching, good memory and flexible characteristics indicate it is a promising candidate for flexible electrochromic displays or electronic paper.