| Summary: | 碩士 === 國立清華大學 === 材料科學工程學系 === 104 === Owing to its high specific capacity (3579 mAh/g), silicon has become one of the most promising anode material candidates for use in lithium ion batteries. However, a 400% volume change during alloying is currently the biggest challenge toward their commercial application. The addition of graphene offers one potential method to overcome this problem. Due to its excellent mechanical properties, graphene is well suited to act as a buffer layer between silicon facilitating its large volume expansion. Hence, a facile route toward the optimization of graphene reduction is required.
In this work, we demonstrate two different approaches leading to more efficient and low cost processes in order to exfoliate and reduce graphene oxide simultaneously within a few minutes. The difference between the two methods is the starting materials. First, the proposed method, so-called “dry exfoliation method” utilizes silicon carbide as an efficient microwave susceptor heat source. The second method, called “wet exfoliation method” uses graphene oxide solution with the addition of a reducing agent. In both cases, under microwave radiation, graphene oxide undergoes a rapid heating and reduction to graphene. To characterize our materials, we utilize Fourier transform infrared spectroscopy (FTIR) and X-Ray photoelectron spectroscopy (XPS), the loss of C=O peaks and OH peaks confirm the reduction of graphene oxide after treatment. Scanning Electron Spectroscopy (SEM) and Transmission Electron Microscopy (TEM) are used to morphologically characterize the material we synthesized.
The cell performances of two different method of reducing graphene oxide are compared, showing capacity values of 1200mAh/g after 150 cycles for r-GO prepared from wet exfoliation method. Furthermore, by using the wet exfoliation method, additional precursors such as copper nanowires can be easily combined into the solution for further material enhancement. We believe this work presents a highly promising technique toward the low-cost production of reduced graphene oxide suitable for future Si based Li-ion battery applications.
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