鋰離子二次電池負極材料表面改質之發展與改良

Development and Improvement of the Lithium Ion Battery Negative Material Surface Modification

吳玉祥(Yu-Shiang Wu) ； 吳俊霖(Chun-Lin Wu) ； 張晏銘(Yan-Ming Chang)

《中華技術學院學報》 31期 (2004/12) Pp. 247-262

https://doi.org/10.7095/JCIT.200412.0247

摘要

一般的商用鋰離子二次電池的負極材料為石墨碳材，可分為人工石墨(Artificial graphite)與天然石墨(Natural graphite)。而人工石墨一般皆使用介穩相球狀碳(Meso carbon micro beads, MCMB)，而MCMB是一種低表面積、高緊密堆積的球狀碳，其結構規則性高，有利於鋰離子之可逆進出碳材料，所以其有庫倫效率高，第一次不可逆小等優點，但由於其必須加熱至2800℃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，降低其在商業上的競爭力。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。但由於在充放電過程中，其電容量會產生第一次不可逆性較大，而造成可逆電容量之降低，為改善此缺點，可利用表面改質(Surface modification)製程，在石墨表面彼覆上一層夫喃樹脂(Furan resin)經熱處理復碳化之非晶質碳材，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與減緩充放電遲滯現象(Hysteresis)。由實驗中得到未彼覆碳材的球狀天然石墨，在經過5次充放電復，所得之不可逆電容量值為18.0%，而在經過彼覆非晶質碳復，其不可逆電容量降為5.8%，由此可見球狀天然石墨彼覆非晶質碳復，確實有效改善石墨本體結構的問題。

關鍵字

鋰離子電池 ； 負極材料 ； 天然石墨 ； 夫喃樹脂

並列摘要

The negative material of commercial lithium ion battery can be divided into the artificial graphite and natural graphite. Artificial graphite comes from meso-carbon micro beads (MCMB) that shows low surface area, high density stacking spherical carbon. Owing to its order structure, lithium ion can insert the carbon material easily that has high coulomb efficiency and small first irreversibility. Because MCMB must be heated to become graphite above 2800℃, it causes high cost for expansive high temperature process that reduces MCMB commercial competitiveness. In this study, the higher first irreversibility of charge and discharge process cause lower capacity. In order to improve this shortcoming, surface modification from Furan resin heat treatment in the spherical nature graphite will be investigated. The amorphous carbon on the graphite surface can suppress lithium complex to intercalate graphite layer that reduce irreversible capacity and slow down discharge hysteresis. From experimental data, the five times irreversible capacity reduces from 18.0% to 5.8% after amorphous carbon coating. It is obvious that carbon coating on the spherical nature graphite improves the graphite negative electrode structure effectively.

並列關鍵字

Lithium ion battery ； Negative electrode ； Natural graphite ； Furan resin