以溶液凝膠法製備矽酸鋰錳添加磷酸鋰錳材料 (1-x)Li2MnSiO4‧xLiMnPO4並探討其電性表現

Investigation of Electrical Performance of (1-x)Li2MnSiO4‧xLiMnPO4 Synthesized by Sol-gel Process

吳閎遂(Wu, Hung Sui)

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(2015年)

摘要

鋰離子電池因具有高能量密度與高功率的特性，近年來成為最有潛力的能源儲存材料。其中矽酸鋰錳陰極材料因為具有300 mAh/g以上的理論電容量而被廣泛研究。但由於矽酸鋰錳很低的電子、離子導電度與結構不穩定的特性，導致循環壽命不佳且電壓平台不明顯的結果。
本實驗是以溶液凝膠法製備矽酸鋰錳，並添加磷酸鋰錳以改善電性。由於磷酸鋰錳的磷酸根與矽酸根都是屬於四面體結構，並且磷酸鋰錳有較佳的導電度與結構穩定性，本身也能參與充放電反應，預期添加後能夠改善矽酸鋰錳的電性表現。
然而不如預期的是當矽酸鋰錳添加磷酸鋰錳後，並無磷酸鋰錳的相生成，反而造成矽酸鋰錳相的結晶度與純度變差。但電性表現仍有大幅的改善，未添加磷酸鋰錳時，以0.05C充放電速度下，放電電容量約100 mAh/g，添加10 %磷酸鋰錳後，放電電容量可達160 mAh/g左右，電壓平台也變得更明顯。

關鍵字

鋰離子電池

並列摘要

Lithium ion battery becomes one of the most promising energy storage systems recently, because of its high theoretical energy density and high power. The Li2MnSiO4 as cathode material has been widely studied because it has high theoretical discharge capacity which is more than 300 mAh/g. However, due to its low electronic and ionic conductivity and structural instability, Li2MnSiO4 has poor cycle life and unobvious voltage platform.
In this experiment, we used sol-gel method to synthesis Li2MnSiO4 and partially substituted with LiMnPO4 in order to improve performance by increasing its conductivity, improving its structural stability, and enhancing electrochemical reactivity.
With the partial substitution of LiMnPO4, there was no LiMnPO4 phase synthesized. The materials remain less Pmn21 phase and more P121/n1 phase. The electrical performances of the one partially substituted with LiMnPO4 is better than that without substitution. The discharge capacity of Li2MnSiO4 which was not substituted was about 100 mAh/g at 0.05C and that substituted by 10 % LiMnPO4 was about 160 mAh/g at 0.05C having more obvious voltage platform as well.

並列關鍵字

lithium ion battery

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