利用鈮摻雜二氧化鈦添加層對多硫化物之化學吸附以提高鋰硫電池電化學性能

Improving the Electrochemical Performance of Lithium–Sulfur Batteries Using an Nb-Doped TiO2 Additive Layer for the Chemisorption of Lithium Polysulfides

鄒宛庭(Wan-Ting Tsou)

指導教授 ： 杜正恭

國立清華大學/工學院/材料科學工程學系/碩士(2018年)

摘要

近年來，由於電動車與電子產品的崛起，市場對於具有高能量密度與低成本的充電電池需求快速增加，相較於傳統電池容量較低的鋰離子電池，具有高理論容量且活性材料成本低廉的鋰硫電池，將主宰為下一世代的鋰離子電池系統。
本研究提出一個簡易的雙層結構電極的設計來減緩多硫化物在電解液中遷移的效應。有別於一般文獻所提出的將具有極性的添加劑混入正極材料的方式，這篇論文將鈮摻雜二氧化鈦塗布在富含硫的正極上，形成一層添加層。此添加層得以利用化學吸附方式，抓住溶於電解液中的多硫化物，避免其穿梭至對電極，提高整體電容量與電池壽命。利用此電極設計，電池第一圈可提供高達1880 mA h g-1 的電容量，與未改質的鋰硫電池相比，有顯著的電性提升。此外，本研究利用XPS進一步驗證鈮摻雜二氧化鈦對於多硫化物的化學吸附反應，進一步證明此添加層對於整體電池之循環壽命、電容量與高電流充放電性能的改善。

關鍵字

鋰硫電池 ； 金屬氧化物添加劑 ； 化學吸附 ； 雙層電極結構 ； 飛梭效應

並列摘要

This study presents a method to suppress the migration of lithium polysulfides in lithium–sulfur batteries by introducing a dual-layer electrode structure. Herein, unlike conventional methods of mixing the polar additives with sulfur/carbon composites, melted sulfur mixed with mesocarbon microbeads are used as the electrode and covered with an additive layer of Nb-doped TiO2/graphite composite via two-step blade coating. By doping TiO2 with Nb, electrical and lithium ion conductivity of TiO2 can be increased, thereby enhancing the redox reaction kinetics. Most importantly, chemisorption of lithium polysulfides to Nb–TiO2 can effectively mitigate the shuttle effect, resulting in higher capacity and longer cycle life. The electrode with the Nb–TiO2 additive layer results in a 1st and 100th cycle specific capacity of 1883 mAh g-1 and 894 mAh g-1, respectively, at 0.1 C (1 C = 1675 mAh), indicating enhanced electrochemical performance as compared with that of bare lithium-sulfur batteries. X-ray photoelectron spectroscopy (XPS) study was conducted to investigate the interaction between polysulfides and Nb–TiO2. The results indicate that the Nb–TiO2–layered electrode efficiently traps polysulfides on the cathode and improves the rate capability, cycle performance, and specific capacity.

並列關鍵字

Lithium sulfur battery ； Metal-oxide additives ； Chemisorption ； Dual-layer structure ； Shuttle effect

參考文獻

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