| Under the pressure of energy issues and environment problems, it has become more important than ever to find an alternative to the traditional fossil fuel energy. During these candidates, battery shows great competitivene ss due to its very high energy conversion efficiency and little pollution. Lithium ion battery, with high output voltage and large specific capacity, has aroused more and more attention. It is an essential issue to improve the capacity and energy density for building better Li-ion batteries, especially considering the urgent need of its applications, such as portable electronic devices, electric vehicles, smart grid, etc. Generally speaking, there are some components that do not release energy in Li-ion batteries-- conductive agent, current collectors and binders, for instance. Thus, the increase in specific capacity and energy density depends largely on the decrease in these electrochemically inert components.In this work, conducting agent and current col lectors composed of super-aligned carbon nanotubes(SACNTs) w ere constructed. It will help a lot to increase the specific capacity and the energy density, because of the highly ordered orientation, clean surface and strong Van der waals interaction of SACNTs. By comparing the performance of electrodes containing different types of conductive agent, it can be concluded that it is the size, aspect ratio, and dispersion state of the additive that matters. Besides, a hybrid conducting network with both high and low aspect fillers exhibits more efficient charge transfer. Based on this conclusion, SACNT films were uniformly introduced in the Li Co O2—Super P composite cathodes by a cold-rolling method, and a hybrid conducting network was formed. Such attempt increas ed the conductivity, as well as the strength, of the electrode with addition of less than 0.01 wt% of SACNTs. As a result, better cycling stability and rate capability were achieved.A new type of flexible CNT current collector with extremely low weight and thin thickness was fabricated by cross-stacking SACNT films. In comparison with metal current collectors, such SACNT films demonstrated better wetting and larger contact area at the electrode/CNT interface, exhibited higher specific capacity, and greatly increased the energy density. Owing to the strong interaction between SACNTs, this work overcame the common problem of too large thickness and expensive cost faced in many carbon-based current collectors in literature. Moreover, considering the weakness o f intrinsic conductivity of SACNT films, a method of evaporation was introduced to form a thin layer of metal on the surface. This modification, with a very little weight and volume increases, significantly reduced the sheet resistance of SACNT films, improved the rate performance further, and helped the CNT current collectors to meet the need of Li-ion batteries with large capacity.A novel electrode based on SACNT films was designed, in which CNT served as conductive agent, binder and current collector. T he weight ratio of the active materials was increased to more than 95%. The reaction kinetics was also improved under the help of the high conductivity, strong strength and porous morphology of the cross-stacked SACNT films. Furthermore, a flexible thin fi lm battery consisting of such new kind of electrode was fabricated, which exhibits a high areal capacity. |
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