Yunyong Li

Nitrogen-Doped Carbon-Encapsulated SnO2@Sn Nanoparticles Uniformly Grafted on Three-Dimensional Graphene-like Networks as Anode for High-Performance Lithium-Ion Batteries

A peculiar nanostructure consisting of nitrogen-doped, carbon-encapsulated (N-C) SnO2@Sn nanoparticles grafted on three-dimensional (3D) graphene-like networks (designated as N-C@SnO2@Sn/3D-GNs) has been fabricated via a low-cost and scalable method, namely an in situ hydrolysis of Sn salts and immobilization of SnO2 nanoparticles on the surface of 3D-GNs, followed by an in situ polymerization of dopamine on the surface of the SnO2/3D-GNs, and finally a carbonization. In the composites, three-layer core-shell N-C@SnO2@Sn nanoparticles were uniformly grafted onto the surfaces of 3D-GNs, which promotes highly efficient insertion/extraction of Li(+). In addition, the outermost N-C layer with graphene-like structure of the N-C@SnO2@Sn nanoparticles can effectively buffer the large volume changes, enhance electronic conductivity, and prevent SnO2/Sn aggregation and pulverization during discharge/charge. The middle SnO2 layer can be changed into active Sn and nano-Li2O during discharge, as described by SnO2 + Li(+) → Sn + Li2O, whereas the thus-formed nano-Li2O can provide a facile environment for the alloying process and facilitate good cycling behavior, so as to further improve the cycling performance of the composite. The inner Sn layer with large theoretical capacity can guarantee high lithium storage in the composite. The 3D-GNs, with high electrical conductivity (1.50 × 10(3) S m(-1)), large surface area (1143 m(2) g(-1)), and high mechanical flexibility, tightly pin the core-shell structure of the N-C@SnO2@Sn nanoparticles and thus lead to remarkably enhanced electrical conductivity and structural integrity of the overall electrode. Consequently, this novel hybrid anode exhibits highly stable capacity of up to 901 mAh g(-1), with ∼89.3% capacity retention after 200 cycles at 0.1 A g(-1) and superior high rate performance, as well as a long lifetime of 500 cycles with 84.0% retention at 1.0 A g(-1). Importantly, this unique hybrid design is expected to be extended to other alloy-type anode materials such as silicon, germanium, etc.

Transparent and Self-Supporting Graphene Films with Wrinkled- Graphene-Wall-Assembled Opening Polyhedron Building Blocks for High Performance Flexible/Transparent Supercapacitors

Improving mass loading while maintaining high transparency and large surface area in one self-supporting graphene film is still a challenge. Unfortunately, all of these factors are absolutely essential for enhancing the energy storage performance of transparent supercapacitors for practical applications. To solve the above bottleneck problem, we produce a novel self-supporting flexible and transparent graphene film (STF-GF) with wrinkled-wall-assembled opened-hollow polyhedron building units. Taking advantage of the microscopic morphology, the STF-GF exhibits improved mass loading with high transmittance (70.2% at 550 nm), a large surface area (1105.6 m2/g), and good electrochemical performance: high energy (552.3 μWh/cm3), power densities (561.9 mW/cm3), a superlong cycle life, and good cycling stability (the capacitance retention is ∼94.8% after 20,000 cycles).

Facile low-temperature synthesis of hematite quantum dots anchored on a three-dimensional ultra-porous graphene-like framework as advanced anode materials for asymmetric supercapacitors

A composite consisting of well-dispersed and ultrafine hematite quantum-dots (∼2.7 nm) anchored on a three-dimensional ultra-porous graphene-like framework (denoted as Fe2O3-QDs–3D GF) has been designed by a facile and scalable strategy. In the composite, the ultra-porous 3D GF with high conductivity and high surface area was used as a conductive matrix with surface defective sites for the controllable growth of uniformly dispersed, ultra-small Fe2O3-QDs. The graphene framework can tightly hold a great amount of Fe2O3-QDs, thereby ensuring high utilization of active materials and the required conductivity to individual Fe2O3-QDs. The ultra-small-sized Fe2O3-QDs anchored on the 3D GF can endow the composite with a superior high surface area and enough active sites for electrochemical reactions, thus giving the composite a large specific capacitance. As expected, the as-prepared Fe2O3-QDs–3D GF electrode exhibited a high specific capacitance of 945 F g−1 at 1.0 A g−1 in a three-electrode system in 2.0 mol L−1 KOH aqueous solution. In addition, high-performance asymmetric supercapacitors have been fabricated with Fe2O3-QDs–3D GF as the anode and 3D hierarchical porous graphene (HPG) as the cathode, and they showed a very high energy density of 77.7 W h kg−1 at a power density of 0.40 kW kg−1 and maximum power density of 492.3 kW kg−1, as well as excellent cycling stability.

NaCl multistage-recrystallization-induced formation of 3D micro-structured ribbon-like graphene based films for high performance flexible/transparent supercapacitors

Individual graphene ribbons, which fully exploit the large surface area of graphene sheets, have been fabricated. Constructing these unique structures into efficient macroscopic functional architectures is an important and challenging step towards practical applications. Here, we produce micro-structured interconnected ribbon-like graphene sheets (MRGs), which were induced by the multistage-recrystallization of NaCl templates in a microwave plasma chemical vapor deposition (MPECVD) system. The MRGs along different directions hang in polygonal graphene walls, which connect with each other forming a three dimensional (3D) transparent and self-supporting graphene film (MRG-GF). The MRG-GF with a large surface area, enhanced flexibility and fast ion/electron transport pathways exhibits improved capacitance (4.88 mF cm−2) and super-long cycle life with good cycling stability (capacitance retention was ∼95.5% after 20 000 cycles). Herein, we provide a novel approach for controlled synthesis of graphene ribbons, and graphene ribbon-based functional structures and composites.

A new kind of water-based nanofluid with a low loading of three-dimensional porous graphene

Abstract In this study, stable water-based heat transfer nanofluid containing a kind of three-dimensional porous graphene (3D PG) has been prepared. For dispersion of 3D PG in water, it is hydrophilic treated by an alkaline method, which is a facile and effective approach in preparing water-soluble graphene by introducing the carboxyl groups (–COOH) as a mild oxidation process using potassium persulfate. The stability and thermal conductive performance of the nanofluid have been investigated with different loading at various temperatures. Experimental results show that the nanofluid can remain highly stability and its enhanced thermal conductivity up to 8–34% can be observed even at lower weight fraction of 0.01–0.07 wt% at room temperature.

A Strapdown Measurement of Vehicle Posture

Vehicle bodywork posture measurement has been a gordian technique in automotive．This paper presented a non-gyro bodywork posture measurement program．Using only one triaxial acceleration transducer with wheel speed encoders it provided a solution of calculating real-time bodywork posture．A lot of streamlining had been made within this program in order to assurance system for real-time performance．Concretely it gave an example of hardware implementation circuit through using LPC1758 as MCU and MMA7260 as triaxial accelerometer, as well as the noise filtering solusion for the circuit．This strapdown measurement has the advantages of high reliability，adaptability and good real-time performance，its precision meets the necessary accuracy requirement of normal application.