Synthesis and Characterizations of Few-Layer Two-Dimensional Nanomaterials and Their Applications for Heat Dissipation and Lithium Ion Batteries

• Main Authors: Wei-Cheng Cheng, 程偉丞
• Other Authors: Wei-Ren Liu
• Format: Others
• Language: zh-TW
• Published: 2019
• Online Access: http://ndltd.ncl.edu.tw/handle/93bfax

碩士 === 中原大學 === 化學工程研究所 === 107 === In recent years, there are many studies focus on two-dimensional materials due to their excellent properties, such as high stability, high conductivity and good electronic properties. Since the interactions between the layers of the bulk material are determined by van der Waals forces, they can be exfoliated easily. Moreover, few-layer two-dimensional materials always have better properties compared to bulk. In our study, a green, facile, low-cost and scalable liquid exfoliation method using jet cavitation was employed to rapidly exfoliate few-layered two-dimensional nanomaterials. We choose the hexagonal boron nitride(h-BN) which has high thermal conductivity, and tungsten diselenide(WSe2), type of transition metal dichalcogenides (TMDs) as our precursors. We successfully prepared few-layered h-BN(FL-hBN) and few-layered WSe2(FL-WSe2) by using jet cavitation. We then applied FL-hBN and FL-WSe2 filler for silicone and as anode materials for lithium-ion battery, respectively. The structure of hexagonal boron nitride is similar to that of graphite. h-BN has many advantages such as exceptional electrical insulation, excellent thermal conductivity and chemical stability, ultralow dielectric constant, and a negative thermal expansion coefficient. We prepared few-layered FL-hBN and analyzed its thickness and the atomic force microscopy (AFM) revealed the average thickness of FL-hBN is about 4.1 nm. Moreover, the specific surface area of FL-hBN is higher than that of h-BN. The h-BN and the as-synthesized FL-hBN were applied as fillers in silicone composite. At a loading of 30 wt.% FL-hBN and h-BN, the thermal conductivities of silicone composites were enhanced by 230% and 189%, respectively. In addition, the composites containing FL-hBN also possessed excellent thermal stability. WSe2 is a graghene-like material. Monolayer WSe2 is a semiconductor material with direct bandgap of ~1.2 eV, it has valuable application in optoelectronic devices. According to atomic force microscopy (AFM), thickness of FL-WSe2 is 9.9 nm. The specific surface area of FL-WSe2 is also higher than that of WSe2. WSe2 and FL-WSe2 were applied as anode for lithium ion battery. The results show that the reversible capacity of FL-WSe2 is 288.6 mAh/g at a current density of 10C, when cycled back to 0.1C, the electrode was able to regain an average capacity of 508.3 mAh/g. The reversible capacity of FL-WSe2 is higher than WSe2 at all current density. We also obtained a reversible capacity of 435.3 mAh/g of FL-WSe2 after 80 cycles. These results show the FL-WSe2 battery possess high reversible capacity performance. In this study, few-layered two-dimensional nano-materials were successfully prepared. They have excellent performance for heat dissipation and lithium-ion battery applications.