探討Ti4O7導電金屬氧化物之添加增進單質硫與碳硫複合材系統下鋰硫電池充放電性能之研究

Investigation of Electrochemical Performance of Lithium-Sulfur Cell by Addition of Ti4O7 Conductive Metal Oxide

余俊緯(YU,CHUN WEI)

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

鋰硫電池具有高達1675 mAh/g的理論電容量以及2600 Wh/kg的能量密度，遠高於傳統鋰離子二次電池的3-5倍之多，此外硫還具有地表含量豐富、環境友善和低成本等優點，因此鋰硫電池被視為是下一世代極具開發前景的儲能材料之一。
本研究嘗試以部分添加Ti4O7導電金屬氧化物，藉由Ti4O7優良的導電性與化學吸附性有效提升鋰硫電池在單質硫與碳硫複合材系統下的效能，本實驗的第一部分為Ti4O7參雜進單質硫的系統中，發現在37.5 %和50 % Ti4O7取代量下表現出較佳的循環壽命，且由阻抗分析中發現適量添加Ti4O7能夠大幅降低單質硫系統下的電荷轉移阻抗；本實驗第二部分為將Ti4O7參雜在碳硫複合材的系統中，其中在25 %和50 % Ti4O7取代量下可降低電池內部電荷轉移阻抗並有效提升電容量和循環壽命表現，且以碳硫複合材作為活物可大幅提升活物利用率，使電性表現明顯優於單質硫系統。實驗的第三部分是以刮刀塗布的方式將Ti4O7與導電碳黑Super P披覆在隔離膜表面，此導電層可作為上集流器加速電子傳遞以及限制液態的鋰硫化合物的擴散，使鋰硫電池在電性及循環壽命上有更好的表現。

關鍵字

鋰硫電池 ； 亞氧化鈦 ； 金屬氧化物

並列摘要

The lithium-sulfur batteries show significant potential for next-generation energy storage systems, due to its high specific capacity of 1675 mAh/g and theoretical energy density of 2600 Wh/kg are 3-5 times higher than conventional lithium ion battery. Furthermore, sulfur show advantages of low cost, environmental benign, and naturally abundant.
The present work attempted to use Ti4O7 conductive metal oxide as an additive in the cathode to increase cycling performance owning to its high electric conductivity and chemical binding of soluble polysulfides. At the first part, the Ti4O7 was introduced to pure sulfur system through slurry mixing process. The results showed that the addition of 37.5 % to 50 % Ti4O7 could improve cycle life and capacity retention. From EIS measurement, we found that the charge transfer resistance was significantly reduced by addition of appropriate amount of Ti4O7. At the second part, the Ti4O7 was introduced to Graphene-S composite system through slurry mixing process. The results showed that the addition of 25 % to 50 % Ti4O7 could reduce charge transfer resistance and improve the capacity performance and cycle life. In addition, using Graphene-S composite as active material could lead to better sulfur utilization than pure sulfur system.
At the third part, the Ti4O7 and conductive carbon black Super P were coated on the commercial polypropylene separator by doctor blade method. The functional coating layer has been investigated to improve the electrochemical performance of lithium-sulfur battery, and served as an upper current collector to facilitate electron transport and a conductive network for trapping and depositing dissolved polysulfides.

並列關鍵字

Lithium sulfur ； Ti4O7 ； Conductive metal oxide

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