軟硬碳披覆天然石墨之鋰離子電池負極材料研究

本研究是以表面改質之碳披覆方式，於天然石墨表面披覆一層非晶質碳膜，來穩定石墨的層間結構，改善鋰離子電池負極材料表面結構與電化學特性，並降低充放電中第一次不可逆性與電容量衰退。實驗以軟碳（煤焦瀝青）與硬碳（酚醛樹脂）作為碳披覆材料，其含量為15wt.%，並將軟碳/硬碳比分別取為10：90、30：70、50：50、70：30、90：10之比例，放入管型爐中通入氮氣，以10°C／min升溫至1100°C持溫3小時熱處理而形成非晶質碳膜。改質前後的表面型態由粗糙變為較平滑，披覆碳材會造成層間距離d（002）的增加與石墨化度降低，以及菱面晶比例增加，而改變石墨的表面結晶特性，以不同比例軟碳（煤焦瀝青）與硬碳（酚醛樹脂）90：10披覆改質後，確實能有效改善石墨表面結構的問題，進而改善其不可逆性及提高循環穩定性。

關鍵字

天然石墨；軟硬碳披覆；表面改質；鋰離子電池

並列摘要

In this study, we reinforced layer structure of nature graphite by coating amorphous carbon on its surface. The process of surface modification is able to improve surface structure and electrochemical property of anode material in lithium-ion battery, and decrease value of the first irreversible capacity and capacity fading. In this experiments, about 15wt.% soft carbon (coal tar pitch) and hard carbon (phenolic resin) were used as coating materials. The soft/hard carbon were prepared in 10:90, 30:70, 50:50, 70:30, 90:10 ratio respectively and homogenous mixed with acetone and graphite. Lastly, the graphite coated was placed in alumina crucible and heated in tubular heater under atmosphere of nitrogen. The temperature was increased in steps of 10°C/min, and amorphous carbon film was kept at 1100°C for 3 hrs. The result of surface modification performed that the graphite surface became smooth after modification, that the d(002) increased, the graphitization degree decreased and the ratio of rhombohedral increased, suggesting the amorphous carbon had homogenous coated on surface of graphite and changed crystalline of graphite surface. The sample composed of soft (coal tar pitch) / hard (phenolic resin) carbon in 90:10 ratio had improved surface structure of graphite, irreversible capacity and recycling stability.

並列關鍵字

natural graphite ； soft/hard carbon coating ； surface modification ； lithium-ion battery

國際替代計量

軟硬碳披覆天然石墨之鋰離子電池負極材料研究

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