水熱法製備鋰離子電池之陰極材料LiCoPO4

Hydrothermal Synthesis of LiCoPO4 Particles as Cathode Materials for Lithium Ion Batteries

何夢璐(He,Monroe)

指導教授 ： 蔡哲正

國立清華大學/工學院/材料科學工程學系/碩士(2016年)

摘要

因鋰離子電池具有能量密度高、放電容量大、循環壽命長、安全性好等特點，成為最有希望的儲能材料之一。其中LiCoPO4因具有高的氧化還原電壓4.8 V和能量密度800 Wh/kg被大量研究。但LiCoPO4也有一些不足之處，電子導電率低，鋰離子傳導率低，電解液在高壓下易分解導致循環電性差。
本實驗用水熱法製備LiCoPO4粉末，分別在220 oC下的溶劑熱法和400 oC下的超臨界流體法兩個體系，并摻雜三價鐵以期改善電性。將三價鐵代替鈷的位置能使材料中多出鋰離子的缺陷，增加鋰離子的擴散速率。
超臨界流體法製備的LiCoPO4顆粒遠小於溶劑熱法製備的，且多片狀結構。在0.1 C下，摻雜10%三價鐵確實能使放電電容量提升一倍。但不如預期的是還沒找到一種合適的方法使片狀結構的LiCoPO4測出實際的電性。

關鍵字

磷酸鋰鈷 ； 水熱法 ； 鋰離子電池

並列摘要

Lithium ion batteries are considered to be one of the most promising energy storage materials because of their high energy density, high discharge capacity, long cycle life and safety. LiCoPO4 cathode material attracts lots of research interests due to high redox potential ( 4.8 V ) and high energy density ( 800 Wh/kg ). However, there are some shortcomings, such as, low electronic conductivity, low lithium ion conductivity, and the decomposition of electrolytes under high potentials, resulting in poor cyclic stability.
LiCoPO4 particles were prepared by hydrothermal method. The syntheses were explored in two conditions: solvothermal process at 220 oC and supercritical fluid method at 400 oC. Fe3+ doping was also conducted in order to improve the electrical performance of LiCoPO4.
LiCoPO4 particles prepared by supercritical fluid method were much smaller than those prepared by solvothermal method, which mainly have sheet structures. Although, poor electrochemical performance were obtained in this experiment due to non-optimized slurry forming processing, Fe3+ doping actually improved the discharge capacity slightly.

並列關鍵字

LiCoPO4 ； hydrothermal ； Lithium ion batteries

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