水熱法合成尖晶石結構之鋰鈦氧負極材料

Spinel Li4Ti5O12 Synthesis via Hydrothermal Process and its Electrochemical Study

斐爾文(Erwin Rodriguez)

指導教授 ： 吳乃立

國立臺灣大學/工學院/化學工程學研究所/碩士(2011年)

https://doi.org/10.6342/NTU.2011.02261

摘要

水熱法為一較親近環境的液相合成法，且此方法有著控制合成顆粒尺寸與形貌的潛力。包括奈米尺寸的方形粒子、奈米薄片及球形二次粒子，這些不同形態的Li4Ti5O12 (LTO)，皆可以用TiO2粉體與LiOH透過水熱水溶性之鈦過氧化物與後續熱處理合成出來，且不同晶相之TiO2皆被當作反應的前驅物。由實驗結果顯示，LTO顆粒型態受到反應溫度、鋰鈦化學計量比、過氧化氫濃度以及ph值之影響甚大。藉由調整這些參數，可控制所合成之粒子為具有均一粒徑分佈之奈米方形粒子、厚度小於10nm之奈米薄片以及由均一奈米粒子所形成之球形二次粒子。奈米結構之LTO粉體能夠縮短鋰離子之擴散路徑並提高電解液與電極之接觸面積，進而提升其在高速充放電時之電容量。奈米薄片型態之LTO在高C-rate下具有極佳之效能，在50 C-rate時能夠達到75%之電容量(124mAh/g)。由實驗結果可知其充放電效能為：奈米薄片＞奈米方形粒子＞奈米薄片所形成之二次粒子＞奈米方形粒子所形成之二次粒子。在大於5 C-rate 之條件下，LTO粉體具極佳之充放電循環效能，且在充放電900圈之後僅損失7%之電容量(奈米方形粒子)。

關鍵字

水熱法 ； 水溶性鈦過氧化物 ； Li4Ti5O12 ； 形貌控制

並列摘要

The hydrothermal synthesis is a soft-solution process, which operates near the ambient condition, and one of its greatest advantages is the possibility to synthesize materials with controlled the size and morphology. Nanocrystalline square particles, nano flakes or spherical secondary particles of Li4Ti5O12 (LTO) have been synthesized from TiO2 powder and LiOH via a hydrothermal treatment of water soluble titanium peroxide followed by thermal treatment. Titanium dioxide (TiO2) as a precursor has been employed in its different phases. The morphology of the resulting LTO products have strongly been found to depend on temperature, stoichiometric ratio of lithium titanium, concentration of hydrogen peroxide, and pH. With the latter parameters, the morphology was controlled obtaining square particles with narrow distribution size, nano flakes with less than 10 nm of thickness, and spherical secondary particles of the letter nano particles. The nanostructured LTO in powders serves to shorten the diffusion distance of lithium ion (path way) and enhances contact area between electrode and electrolyte, thus improving its high rate capability. Great performance at high C-rate has been delivered by the nano flakes morphology of LTO, which achieved 75 % (124 mAhg-1) of the capacity at 50 C-rate. The results show that the rate capability is in the following order: nano flakes powder > nano square particles powder > secondary particle of nano flakes powder > secondary particle of square particles powder. Upon cycling at 5 C-rate, all the LTO powders show good cycle stability, losing less than 7 % capacity after 900 cycles (for the square particles).

並列關鍵字

Hydrothermal synthesis ； Soluble titanium peroxide ； Li4Ti5O12 ； morphology control

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