以二硫化鈷作為鋰硫電池添加劑之電化學性能研究

Electrochemical Performance of Lithium-Sulfur Cell by Addition of Cobalt Disulfide

黃鈺家(Yu-Chia Huang)

指導教授 ： 蔡哲正 ； 吳振名

國立清華大學/工學院/材料科學工程學系/碩士(2017年)

摘要

由於鋰硫電池具備高能量密度以及理論電容量等優秀的電性表現，該種儲能系統被漸漸受到重視。然而，目前鋰硫電池尚未能商業化，其原因包含硫本身的絕緣性，以及反應過程中，中間產物長鏈鋰硫化合物易溶於有機電解液當中造成活性物質的流失，進而導致電容量降低且壽命下降等。
本研究嘗試以二硫化鈷CoS2為添加劑，藉由其好的導電性與對長鏈鋰硫化合物之化學吸附性，提升鋰硫電池的循環壽命。實驗方法為先以水熱合成CoS2，並將其以部分取代電極漿料中導電Super P的方式引入碳硫複材以及單質硫電池系統。結果顯示，在這兩種系統當中若分別加入適量CoS2，即能表現出較佳的循環壽命，並維持一定的電容量水準。
此外，本實驗同樣以簡單水熱法方式，成功將原1.5微米大小之CoS2縮小至450 奈米，也發現若添加的CoS2粒徑縮小，意即增加吸附表面積，除循環壽命表現優良，更能降低電池內部阻抗並提升電容量。

關鍵字

鋰硫電池 ； 過渡金屬硫化物 ； 二硫化鈷

並列摘要

Lithium-sulfur (Li-S) batteries are receiving increasing attention due to their extraordinary performances. However, the insulating nature of sulfur and the “shuttling mechanism” caused by the dissolution of polysulfide in organic electrolytes have limited their practical applications.
Herein, we used cobalt disulfide (CoS2) as an additive to improve cycling performance owning to its high electric conductivity and chemical binding of the polysulfide. Hydrothermally synthesized CoS2 was introduced to sulfur-carbon composite and pure sulfur cells through slurry mixing process. The results showed that with a certain amount of CoS2 in cathode slurry could prolong cycle life of the cells and increase their stability without sacrificing capacity performances.
Furthermore, incorporating CoS2 with smaller particle sizes, which was successfully decreased from 1.5 μm to 450 nm by also a hydrothermal process, could provide more surface areas for depositing polysulfide, thus reducing charge transfer resistance and therefore enhance capacity and cycle life.

並列關鍵字

Lithium-Sulfur ； transition metal sulfide ； cobalt disulfide

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