Jiayou Tao

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.

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.

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.

Freestanding and flexible graphene wrapped MnO2/MoO3 nanoparticle based asymmetric supercapacitors for high energy density and output voltage

Asymmetric supercapacitors (ASC) based on freestanding membranes with high energy density and high output voltage by a simple pre-reduced and vacuum filtering method are reported. Reduced graphene oxide (rGO) coated MnO2 nanospheres and rGO coated MoO3 nanoparticle composites are selected as the positive and the negative materials of the devices, respectively. The ASC has a high operation voltage window of 2.0 V in a hydrogen electrolyte, a high energy density of 34.6 mW h cm−3 at a power density of 100 mW cm−3, and a high volumetric capacitance of 62.7 F cm−3 at a current density of 0.1 A cm−3. Especially, the ASC exhibits an excellent cycling performance of 94.2% capacitance retention after over 3000 cycles. This strategy of designing the hybridized structure for freestanding and flexible ASC provides a promising route for next-generation supercapacitors with high energy density and high output voltage.

Enhanced photo-response properties of a single ZnO microwire photodetector by coupling effect between localized Schottky barriers and piezoelectric potential.

The coupling effect between localized Schottky barriers (SBs) and piezoelectric potential that impact the photo-response properties of a single ZnO microwire (MW) photodetector (PD) is studied. Localized SBs is introduced by Au NPs decoration. The negatively charged Au NPs deplete more carriers near the ZnO surface, which raises the SB height and sharply reduces the recover time of the PD from 142.4 s to 0.7 s. Moreover, after applying the compressive strain, the band structure of ZnO MW changes and piezoelectric potential generates, which further raises the SB height, thickens the depletion region and improves photo-response properties of the detector. The dark current is reduced by about 5 orders and its on/off current ratio increased by about 6 orders, which decreases the power consumption of the detector significantly. Under the above coupling effect between piezoelectric potential and localized SBs, the recover time of the detector is further reduced to 0.1 s ultimately. This work suggests that rational integration of localized SBs and piezoelectric potential is a viable approach to get ZnO MW PDs with high on/off ratio, ultrafast response speed and low power consumption.