리튬 이온 전지 음극물질로서의 대면적 실리콘 나노와이어 및 실리콘아산화물 나노구조 제작

Abstract

The size of anode materials is closely related with Li-ion battery performance. In nano-size systems the distances which Li+ must diffuse are decreased. These size effects

large surface areas, and fast diffusion rates

can play a large role in improving the performance of Li-ion batteries. And the benefit of Si materials as Li-ion battery anodes is highest known theoretical charge capacity (4,200mAh/g

4). The use of Si materials as anode in Li-ion batteries is, however, still hindered from severe volume changes, 400%, during Li insertion/extraction. It is leading to poor cycling performance. So, we use more suitable SiOx nanostructure as Li-ion battery anodes than Si nanostructureIn this thesis, we introduce two kinds of growth method of large scale synthesis of Si nanowires and SiOx nanostructures for using Li-ion battery anodes. First, Si nanowires were synthesized by catalyst-assisted chemical vapor deposition. Using this method, we can obtain single-crystalline Si nanowires. We then demonstrate the fabrication of intrinsic and doped single crystalline Si nanowire arrays with various height and surface roughness through metal-assisted chemical etching. Lastly, we synthesis of SiOx/NiSix core-shell nanowires. During charge/discharge, Li2O plays a structural buffering role to minimize the mechanical stress. Furthermore, electrically conducting and electrochemically inactive NiSix nanowire contributes to enhancing the cyclic behaviors of Li-ion batteries, where core matrix act as fast electron supplier. We have achieved the highly reversible capacity over 1800 mAh/g with its stable cyclic retention.