消費性電子產品之微小化，對高能量密度鋰離子電池產生強烈之需求。從行動電話、數位相機至筆記型電腦等，國內每年對於鋰離子電池之需求量約兩億顆，市場產值超過十億美金。 LiCoO2 為目前鋰離子電池市售材料中使用最廣泛之陰極材料，然而其可逆電容量不高，且在充電截止電壓大於4.3 伏特時，其陰極材料的結構會崩解，且金屬鋰會從陰極材料中析出，導致有安全上之疑慮。LiFePO4 為新型的陰極材料，其優點為成本低、安全性高、環境污染低與允許大電流充放電等特性，且在結構上允許鋰完全地釋出，故熱安全性遠高於LiCoO2 與LiNi0.8Co0.2O2 陰極材料，非常適合於大型電動車應用。但該材料量產困難、導電度低與鋰離子擴散慢等缺點，造成應用瓶頸。本計畫乃利用高溫固態法，使用不同種類的碳源，製備一系列之 LiFePO4/C 複合陰極材料，以及利用金屬摻雜改質LiFePO4 陰極材料，探討不同種類碳源、金屬元素與材料顆粒尺寸等因素，對於材料導電度差異與電池性能之影響。此外，亦研究上述陰極材料之安全性與崩解機制，探討其改善原因與電池安全性之關係。藉由陰極材料晶體結構之鑑定、充放電測試等研究，以探討製程最適化之條件，並為了瞭解鋰離子在嵌入釋出於材料時之反應動力學，將佐以循環伏安法與交流阻抗法等進行電化學鑑定分析。希冀透過此計劃，能開發出應用於大型電動車用之鋰離子電池陰極材料，並提高本國關鍵性物料及鋰離子電池產業之競爭力，期能提升我國在國際鋰離子電池市場之佔有率。 ; Miniaturization of consumer electronics has created a strong demand for high energy density systems of lithium-ion batteries (LIBs). From cellular phones and digital cameras to notebook PCs, the annual domestic demand for LIBs exceeds two hundred million cells, which translates into a multi-billion USD market. LiCoO2 is the most widely used commercial cathode material for LIBs. However, it suffers from severe limitations in cell capacity and safety due to overcharge problems, which occur when the cut-off charge potential exceeds 4.3 volts and metallic lithium can be electrodeposited from LiCoO2. The formation and presence of metallic lithium may create a fire hazard during extreme use. LiFePO4 is considered an attractive cathode material for lithium batteries. Other advantages of LiFePO4 include low price, natural abundance and environmental friendliness of iron precursor materials, better thermal stability of the olivine than LiCoO2 and LiNi0.8Co0.2O2, and the battery industry’s familiarity with iron oxide chemistry. However, factors such as conductivity and synthesis condition must be addressed before the cathode material can be considered for challenging requirements as in electric vehicles. In this proposal, we exploit the solid-state technique for the synthesis of LiFePO4/C composite cathode materials from differenst carbon sources, and modify the LiFePO4 cathode materials by metal dopping. We investigate the effects such as different carbon sources, metal elements and particle size distribution on the conductivity and cell performance. Furthmore, we will study the cell safety and decomposition mechanism of LiFePO4 cathode materials, to improve the related cell performance, and correlate the improvement to cell safety. The structural and morphological features of the cathode materials will be correlated to their electrochemical performance in order to optimize the performance parameters. The mechanism of the intercalation-deintercalation processes in these materials will be examined by CV and AC impedance techniques. The goal of the study is to produce economic and performance benefits that will help local industrial players make a quantum leap in market competitiveness. ; 研究期間 9708 ~ 9807
