Congxiang Lu

A three dimensional vertically aligned multiwall carbon nanotube/NiCo2O4 core/shell structure for novel high-performance supercapacitors

Three dimensional (3D) vertically aligned structures have attracted tremendous attention from scientists in many fields due to their unique properties. In this work, we have built the 3D vertically aligned carbon nanotube (CNT)/NiCo2O4 core/shell nanoarchitecture via a facile electrochemical deposition method followed by subsequent annealing in air. The morphology and structure have been in-depth characterized by SEM, TEM, XRD and Raman spectroscopy. Impressively, when used as the electrode material in a 6 M KOH electrolyte, the vertically aligned CNT/NiCo2O4 core/shell structures exhibit excellent supercapacitive performances, including high specific capacitance, excellent rate capability and good cycle stability. This is due to the unique 3D vertically aligned CNT/NiCo2O4 core/shell structures, which support high electron conductivity, large surface area of NiCo2O4 and fast ion/electron transport in the electrode and at the electrolyte–electrode interface. Furthermore, the synthesis strategy presented here can be easily extended to fabricate other metal oxides with a controlled core/shell structure, which may be a promising facile strategy for high performance supercapacitors, and even advanced Li-ion batteries.

High-Performance Microsupercapacitors Based on Two-Dimensional Graphene/Manganese Dioxide/Silver Nanowire Ternary Hybrid Film

Microsupercapacitors (MSCs), as one type of significant power source or energy storage unit in microelectronic devices, have attracted more and more attention. However, how to reasonably design electrode structures and exploit the active materials to endow the MSCs with excellent performances in a limited surface area still remains a challenge. Here, a reduced graphene oxide (RGO)/manganese dioxide (MnO2)/silver nanowire (AgNW) ternary hybrid film (RGMA ternary hybrid film) is successfully fabricated by a facile vacuum filtration and subsequent thermal reduction, and is used directly as a binder-free electrode for MSCs. Additionally, a flexible, transparent, all-solid state RMGA-MSC is also built, and its electrochemical performance in an ionic liquid gel electrolyte are investigated in depth. Notably, the RGMA-MSCs display superior electrochemical properties, including exceptionally high rate capability (up to 50000 mV·s(-1)), high frequency response (very short corresponding time constant τ0 = 0.14 ms), and excellent cycle stability (90.3% of the initial capacitance after 6000 cycles in ionic liquid gel electrolyte). Importantly, the electrochemical performance of RGMA-MSCs shows a strong dependence on the geometric parameters including the interspace between adjacent fingers and the width of the finger of MSCs. These encouraging results may not only provide important references for the design and fabrication of high-performance MSCs, but also make the RGMA ternary hybrid film promising for the next generation film lithium ion batteries and other energy storage devices.

In situ fabrication of three-dimensional, ultrathin graphite/carbon nanotube/NiO composite as binder-free electrode for high-performance energy storage

Metal oxides have attracted considerable attention as promising electrode materials for energy storage, but the use of metal oxides for electrodes still faces challenges such as attaining high capacity, good cycle stability, and high-rated performance. Therefore, rational design of electrode architectures and assembling metal oxides into desired structures to further enhance electrochemical performance is necessary. Here, novel 3D electrode architectures consisting of 3D ultra-thin graphite film (UGF)/carbon nanotubes (CNTs) uniformly covered by NiO nanosheets are successfully constructed by a chemical vapor deposition and subsequent electrodeposition, which are directly used as bind-free electrodes for supercapacitors and Li-ion batteries. In such composite structures, 3D UGF/CNTs serve as substrates for NiO nanosheet decoration, and act as spacers to stabilize the composite structure, making the active surfaces of NiO nanosheets accessible for electrolyte penetration and accommodating volume changes during charge/discharge processes. As expected, 3D UGF/CNTs/NiO as electrode material for supercapacitors showed high specific capacitance (750.8 F g−1 at current density of 1 A g−1), superior rate performance (capacitance of 575.6 F g−1 at 10 A g−1) and excellent cycle stability (no decay after 3000 cycles). Moreover, the 3D CNTs/UGF/NiO composite also exhibited enhanced lithium storage properties as anode materials for Li-ion batteries.

Paper-based all-solid-state flexible micro-supercapacitors with ultra-high rate and rapid frequency response capabilities

Paper-based flexible supercapacitors (SCs) have attracted great attention as they enable the realization of next-generation bendable, light-weight, and environmentally-friendly portable electronics. However, conventional paper-based SCs adopt a sandwich-like structure suffering from poor rate performance, slow frequency response and difficulty in direct integration with other micro-devices. We report here for the first time paper-based all-solid-state flexible planar micro-supercapacitors (MSCs) using poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS)-CNT/Ag as the electrode material by the inkjet printing technique. The as-fabricated paper-based all-solid-state flexible MSCs deliver the best rate capability among all reported paper-based MSCs/SCs (up to 10 000 mV s−1), fast frequency response (relaxation time constant τ0 = 8.5 ms), high volumetric specific capacitance (23.6 F cm−3) and long cycle stability (92% capacitance retention after 10 000 cycles), which shows a strong dependence on the film thickness and the interdigitated spacing between neighbouring fingers, respectively. Furthermore, the series and parallel connections reveal that the as-prepared paper-based MSCs obey the basic theorem of series and parallel connections of capacitors, respectively. The combination of the simple fabrication technology and excellent performances presented here not only make paper-based all-solid-state flexible MSCs an attractive candidate for powering future flexible portable electronics, but also provide important references for the design and fabrication of other high-performance flexible energy storage devices.

Re-ordering Chaotic Carbon: Origins and Application of Textured Carbon

Formation of nanocrystals with preferred orientation within the amorphous carbon matrix has attracted lots of theoretical and experimental attentions recently. Interesting properties of this films, easy fabrication methods and practical problems associated with the growth of other carbon nanomaterials such as carbon nanotubes (CNTs) and graphene gives this new class of carbon nanostructure a potential to be considered as a replacement for some applications such as thermal management at nanoscale and interconnects. In this short review paper, the fabrication techniques and associated formation mechanisms of these nanostructured films have been discussed. Besides, electrical and thermal properties of these nanostructured films have been compared with CNTs and graphene.

Droplet based lab-on-chip microfluidic Microsystems integrated nanostructured surfaces for high sensitive mass spectrometry analysis

We present in this paper a microsystem coupling electrowetting on digital microfluidic and nanostructured surfaces for matrix-free Laser Desorption/Ionization Mass Spectrometry (LDI-MS) analysis of small biomolecules. Silicon nanowires are processed to form highly sensitive pads for LDI analysis and also to produce superhydrophobic surfaces for enhanced transfer of droplets containing the analytes to the analyzing pads. By this way, analysis of low molecular weight compounds with high sensitivity can be achieved. In addition, wetting properties of carbon nanotubes surfaces are investigated in the perspective of further increasing the detection performances.