天然石墨呋喃樹脂碳材披覆改質之鋰離子電池負極材料開發

Development of Carbon Coating Graphite Prepared from Natural Graphite and Furan Resin as Anodes for Lithium Batteries

一般商用鋰離子電池的負極材料為石墨，可分為人工石墨與天然石墨。而人工石墨一般皆使用介穩相球狀碳(MCMB)，但由於其必須加熱至2800°C 以上方能產生石墨化，需設備昂貴的石墨化爐，因而造成生產成本過高。故本實驗針對將片狀天然石墨，利用氣流粉碎機所製成之球狀天然石墨進行研究，來降低其製造之成本。但天然石墨由於在充放電過程中，其不可逆性電容量會較大，為改善此缺點，可利用表面改質製程，在石墨表面披覆上一層呋喃樹脂(furan resin)經熱處理後碳化之非晶質碳材，透過這層非晶質碳膜，可以抑制鋰錯化合物嵌入石墨層間，來降低其不可逆電容量。實驗証明披覆30wt%呋喃樹脂的球狀天然石墨，除了可提高電容量由282mAh/g 至305mAh/g 外，更降低第一次不可逆性由7.0%至4.3%。

The negative electrode material in a commercial lithium ion batterycan be divided into artificial graphite and natural graphite. Artificialgraphite comes from meso-carbon micro beads (MCMB) which shows lowsurface area and high density stacking. Because MCMB must be heatedabove 2800°C to become graphite, it causes high cost expensive hightemperature processes that reduce MCMB commercial competitiveness. Inthis study, the higher first irreversibility of charge and discharge processcauses lower capacity. In order to improve on this shortcoming, surfacemodification from furan resin heat treatment to spherical natural graphitewill be investigated. The amorphous carbon on the graphite surface cansuppress the lithium complex into an intercalate graphite layer that reducesirreversible capacity. From experimental data, the first irreversibility reduces from 7.0% to 4.3% and capacity from 282mAh/g to 305mAh/gafter amorphous carbon coating.