- 期刊
天然石墨負極材料二次包覆表面改質對鋰電池之電性影響
Electrochemical Impact in Natural Graphite as Anode Material of Double Coating Surface Modification for Lithium Ion Batteries
摘要
市面上的鋰離子電池負極材料大都為石墨碳材，分別是天然石墨、人工石墨與中間相碳微球（MCMB）。天然石墨具有較高的電容量特性，卻礙於比表面積（BET）較大、不可逆電容量逐漸升高的缺點，使得天然石墨的應用受到限制。本研究是以天然石墨作表面改質的二次包覆法，將天然石墨粉過篩、研磨、混製至約20μm粒徑，再利用酚醛樹脂5 wt.%、10 wt.%、15 wt.%等不同比例與天然石墨混合成漿狀，並利用噴霧乾燥製成粉體。由於粉體經過碳化熱處理，使得天然石墨比表面積明顯增加，因此再用聚苯乙烯磺酸5 wt.%與10 wt.%進行二次包覆，可降低比表面積的問題。結果顯示當天然石墨先包覆酚醛樹脂10 wt.%熱處理碳化後後，再二次包覆5 wt.%聚苯乙烯磺酸，其第一次放電電容量為360 mAh/g，第一次不可逆性由13.9%降到8.4%，比表面積由7 m2g-1降至2 m2g-1，其50 次後之庫倫效率均可達到99%以上。
並列摘要
The anode material of lithium ion secondary batteries in the market is graphite carbon material, including artificial and natural graphite. Natural graphite shows better capacitance characteristics; however, the application is limited due to the flaws of its larger specific surface area (BET) and its gradually increasing irreversible capacity. This study used secondary coating method with natural graphite as the surface modification. Sifted, the natural graphite powder was grounded, and mixed into approximate 20μm particle diameter, then the filtered graphite powder was mixed into paste with different proportions (10 wt.%, 15 wt.%, 20 wt.%, and 25 wt.%) of phenolic resin, finally the paste was made into coating powder by spray dryer. The specific surface area was enlarged since the natural graphite powder went through carbonization heat treatment, therefore we used 5 wt.% of polystyrene sulfonate to coat the natural graphite to decrease the specific surface area and solved the problem. The study analyzed the difference in the irreversible capacity under different proportion of phenolic resin and whether it's coated by polystyrene sulfonate. The experiment proved that the natural graphite secondary coating method can reduce the irreversible capacity and enhance the capacity of the battery at the same time.