Lu Yue

Hierarchically porous carbon foams for electric double layer capacitors

The growing demand for portable electronic devices means that lightweight power sources are increasingly sought after. Electric double layer capacitors (EDLCs) are promising candidates for use in lightweight power sources due to their high power densities and outstanding charge/discharge cycling stabilities. Three-dimensional (3D) self-supporting carbon-based materials have been extensively studied for use in lightweight EDLCs. Yet, a major challenge for 3D carbon electrodes is the limited ion diffusion rate in their internal spaces. To address this limitation, hierarchically porous 3D structures that provide additional channels for internal ion diffusion have been proposed. Herein, we report a new chemical method for the synthesis of an ultralight (9.92 mg/cm3) 3D porous carbon foam (PCF) involving carbonization of a glutaraldehydecross-linked chitosan aerogel in the presence of potassium carbonate. Electron microscopy images reveal that the carbon foam is an interconnected network of carbon sheets containing uniformly dispersed macropores. In addition, Brunauer–Emmett–Teller measurements confirm the hierarchically porous structure. Electrochemical data show that the PCF electrode can achieve an outstanding gravimetric capacitance of 246.5 F/g at a current density of 0.5 A/g, and a remarkable capacity retention of 67.5% was observed when the current density was increased from 0.5 to 100 A/g. A quasi-solid-state symmetric supercapacitor was fabricated via assembly of two pieces of the new PCF and was found to deliver an ultra-high power density of 25 kW/kg at an energy density of 2.8 Wh/kg. This study demonstrates the synthesis of an ultralight and hierarchically porous carbon foam with high capacitive performance.

One-step in situ synthesis of ultrathin tungsten oxide@carbon nanowire webs as an anode material for high performance

A novel ultrathin W18O49@carbon nanowire web anode material for high performance lithium-ion batteries is synthesized via a facile one-step solvothermal method. A carbon layer is uniformly coated on ultrathin W18O49 nanowire bundles. The electrochemical properties are analyzed by cyclic voltammetry, galvanostatic charge/discharge cycling and electrochemical impedance. The W18O49@carbon nanowire web electrode exhibits a high lithium storage capacity of 889 mA h g−1 after 250 cycles at 200 mA g−1, which is the best cycling performance among the tungsten oxide anode materials used in lithium-ion batteries reported to date. The improved electrochemical performance can be ascribed to the incorporation of carbon and the unique ultrathin nanowire web architecture of the nanocomposite.

Layer-by-layer assembly modification to prepare firmly bonded Si–graphene composites for high-performance anodes

A new nanocomposite of Si nanoparticles homogenously encapsulated in a graphene composite was prepared by a facile layer-by-layer (LBL) assembled modification method, followed by an electrostatic attraction directed self-assembly approach and thermally reduced process. The wrinkled graphene sheets were assembled into a three-dimensional network and covered the surface of the highly dispersed Si nanoparticles well. The as-prepared Si–graphene composite exhibited good electrochemical performance as an anode material in lithium-ion batteries, showing a stable reversible capacity of 1150 mA h g−1 with a high capacity retention rate of 92.0% over 100 cycles and high rate capability (840 mA h g−1 at 3000 mA g−1).

ZnO Nanocrystals as Anode Electrodes for Lithium-Ion Batteries

ZnO nanocrystals were synthesized via a thermal decomposition method. X-ray diffraction, transmission electron microscopy, and photoluminescence were used to investigate the composition and nanostructure of the material. Compared with commercial ZnO nanoparticles, ZnO nanocrystals showed higher lithium storage capacity and better cycling characteristics and exhibited a reversible discharge capacity of 500 mAh g−1 after 100 cycles at 200 mA g−1.