硼元素對人工石墨奈米碳管性質之影響與鋰離子電池應用研究

BORON DOPING EFFECTS ON THE GROWTH OF ARTIFICIAL GRAPHITE AND CARBON NANOTUBE AND THEIR APPLICATIONS IN LITHIUM BATTERY

本研究目的是以熔融析出石墨（dissolution precipitation graphite，DPG）製程製備含硼之人工石墨，探討硼引發的物理化學效應及鹽酸酸洗人工石墨後其物理性質的變化，並將人工石墨應用於鋰離子二次電池之負極材料，評估其電池性能表現。經過XRD分析、Rietveld method精算與拉曼光譜分析之後，結果發現鹽酸酸洗處理過後的人工石墨，擁有更好的結晶性及更高的石墨化度，使得應用在鋰離子二次電池負極材料上的電池性能，表現出高電容量、高庫倫效率及長充放電循環次數，硼含量300ppm之酸洗處理後人工石墨（BH300）有最高電容量505mAh/g。研究結果證明硼引發之物理化學效應為奈米碳管生成驅動力之一，且鹽酸酸洗DPG製程之人工石墨的確能夠改善其物理性質，並在鋰離子二次電池的電池表現上得到最佳的例證。

The material investigated in this study is artificial graphite, including boron fabricated by the DPG process. The boron-triggering mechanochemical effect and physical properties of artificial graphite cleaned by HCl were studied. The performance of a lithium ion secondary battery, using artificial graphite as anodic material, was also estimated. From XRD analysis, Rietveld method refinement and Raman spectra analysis experimental results, artificial graphite cleaned by HCl displays better crystallization and higher graphitization. These two results increased battery performance, in areas such as high capacity, high coulomb efficiency and long charge-discharge cycles. For example, BH300 has the highest energy density at 505mAh/g. This study has proved that HCl cleaning treatment indeed improves the physical properties of artificial graphite. For a lithium ion secondary battery, artificial graphite is a good candidate for anode material.