Energy & Environmental Science
We report the template-directed synthesis of sulphur-carbon nanotubes and their use to form a membrane that is binder-free, highly conductive and flexible. This nanostructured membrane is used as a self-supporting cathode without metal current-collectors for Li-S batteries. The membrane cathode has a high electrical conductivity and renders a long life of sulphur of over 100 charge-discharge cycles. High discharge capacity of sulphur was attained at 712 mA h g(sulphur)(-1) (23 wt% S) and 520 mA h g(sulphur)(-1) (50 wt% S) at a high current density (6 A g(sulphur)(-1)). The overall capacity of the flexible cathode correspondingly reaches 163 mA h g(-1) (23 wt% S) and 260 mA h g(-1) (50 wt% S). These results demonstrate the great potential of this nanostructured flexible membrane as a cathode for Li-S batteries with fast charge-discharge performance and long life.
关键词:
rechargeable lithium batteries;positive electrode materials;cell;temperature;composites;capacity;oxide
A.H. Salama
材料科学技术（英文）
Li-doped p-type ZnO ceramics were prepared by conventional methods according to the chemical formula Zn1-x LixO2 where x=0.5, 1.0, 1.5 and 2.0 mole fraction, respectively. The crystal structures of the prepared samples were studied by X-ray diffraction analysis. The dielectric properties (including dielectric constant ε'
and dielectric loss ε") and dc-electrical conductivity [σ(Ω-1·cm-1)] were investigated. The dielectric constant ε' was sharply decreased at the low frequency range and independent on frequency at high frequency range. Otherwise, the dielectric loss "00 varied with frequency and showed absorption peak located from 200 Hz to
4 kHz and moved to higher frequency as the concentration of Li+ doped increased. It was found that dc-electrical conductivity log¾ varied from -9 to-5 and the energy gap width were calculated by using Arrhenius equation. The p-type conductivity of Li-doped ZnO may be attributed to the formation of a LiZn-Lii donor complex, which is limited by reducing the amount of Lii.
关键词:
P-type ZnO ceramics
Express Polymer Letters
The state-of-art and key problems of carbon nanotube (CNT) based polymer composites (CNT/polymer composites) including CNT/polymer structural composites and CNT/polymer functional composites are reviewed. Based on the results reported up to now, CNTs can be an effective reinforcement for polymer matrices, and the tensile strength and elastic modulus of CNT/polymer composites can reach as high as 3600 MPa and 80 GPa, respectively. CNT/polymer composites are also promising functional composite materials with improved electrical and thermal conductivity, etc. Due to their multi-functional properties, CNT/polymer composites are expected to be used as low weight structural materials, optical devices, thermal interface materials, electric components, electromagnetic absorption materials, etc. However, the full potential of CNT/polymer composites still remains to be realized. A few key problems, such as how to prepare structure-controllable CNTs with high purity and consistently dependable high performance, how to break up entangled or bundled CNTs and then uniformly disperse and align them within a polymer matrix, how to improve the load transfer from matrix to CNT reinforcement, etc, still exist and need to be solved in order to realize the wide applications of these advanced composites.
关键词:
polymer composites;carbon nanotubes;mechanical properties;electrical;properties;thermal properties
