Li4Ti5O12為尖晶石(spinel)結構的氧化物，且為零應變材料而具有良好的循環性能。因結構穩定性及足夠安全性，Li4Ti5O12深具應用發展潛力之新型鋰離子電池用負極材料。然而，導電性不佳導致在大電流充放電性能差。依缺陷化學觀點，藉電荷補償效應，摻雜異價元素可提升Li4Ti5O12之導電性。同時透過低氧分壓氣氛形成氧離子空缺，增加其帶負電的電子濃度。因此本研究以固相反應法合成高價數過鍍金屬Nb摻雜Li4Ti5O12改善此材料之導電特性，同時以還原氣氛(10% H2/Ar)合成材料得到更佳的導電效應。
另一方面，本研究將電極材料透過射頻磁控濺鍍法成長Li4Ti5O12薄膜。同時，透過濺鍍參數的改變探討薄膜其成長速率及組成之影響，並將最佳參數製備探討合成氣氛對Li4Ti5O12薄膜電化學行為的影響。
由XRD結果顯示由於還原氣氛下氧空缺之形成，促使Nb摻雜Li4Ti5O12的溶解度提升。由導電性的量測顯示還原氣氛下合成Li4Ti5O12導電性可提高約一百倍，空氣下合成之Li4Ti5O12導電性為1.72 × 10-7 Scm-1，還原氣氛下合成之Li4Ti5O12導電性為1.17 ×10-5 Scm-1。然而Nb摻雜Li4Ti5O12結果顯示在空氣下合成之Li4Ti4.95Nb0.05O12導電性無明顯提升。對於不同氣氛下高價數Nb5+取代Ti4+之結果，顯示空氣下主要以鈦空缺的形成來作補償效應，而還原氣氛下則是透過電子產生。
空氣下合成Li4Ti4.95Nb0.05O12，由於Nb5+取代Ti4+，由於離子半徑的不同，晶格常數增加，可讓鋰離子能有效的在材料內部擴散。而還原氣氛下合成Li4Ti5O12促使電子透過混合Ti3+/Ti4+價態的產生，電子導電性提升。
由放電速率測試結果顯示，當放電速率達到10C，空氣下合成之無摻雜Li4Ti5O12電容量已衰退到約130 mAhg-1，而Li4Ti4.95Nb0.05O12電容量為約145 mAhg-1；還原氣氛下合成之無摻雜Li4Ti5O12電容量為約150 mAhg-1且Li4Ti4.95Nb0.05O12的電容量可達到156 mAhg-1。透過交流阻抗法分析結果顯示鋰離子擴散係數隨晶格常數增加而增加。本研究結果證實以還原氣氛使Li4Ti5O12 的導電性提升以及鋰離子擴散行為的改善較摻雜Nb的效果佳。
為了探討Li4Ti5O12電極充放電過程中鋰離子嵌入嵌出過程中電子傳遞與鋰離子擴散行為，本研究以Li4Ti5O12 與鋰金屬間之界面反應進行導電率動態變化量測。同時由Li4Ti5O12對典型的La0.56Li0.33TiO3固態電解質材料個別做比較下，結果顯示Li4Ti5O12與鋰金屬間界面反應之導電性提升速率較La0.56Li0.33TiO3慢。此現象可歸因於鋰離子嵌入位置之空間不同，La0.56Li0.33TiO3為鈣鈦礦(perovskite)結構，鋰離子填入A位置空缺中之空間較尖晶石Li4Ti5O12之八面體位置大，導致鋰離子能有效的在材料內部擴散。因此證實為了改善電極材料的導電性質，除了提升其電子導電率，鋰離子擴散速率的提升更能改善材料電化學特性。
另一方面，本研究將電極材料透過射頻磁控濺鍍法成長Li4Ti5O12薄膜。探討濺鍍參數對薄膜其成長速率及組成之影響，結果顯示隨著氧氣分率降低以及射頻功率提升，薄膜成長速率增加。然而氧氣分率過低，雖可提升薄膜成長速率卻會使得因濺鍍過程中缺氧而導致鈦原子游離而濺鍍於基板；過高的射頻功率雖可提升薄膜成長速率卻由於再濺鍍效應導致結晶性降低。由鋰含量、氧氣分率及射頻功率的改變可得到最佳的鍍膜參數。
為了探討在相同薄膜粒徑下合成氣氛對Li4Ti5O12薄膜電化學行為的影響，進行充放電量測。首次充放電超過其理論電容量(175mAhg-1)，推測額外的電容量為非晶相(amorphous)的TiO2所貢獻。合成氣氛熱處理對薄膜電容量的影響之原因與Li4Ti5O12粉末影響相同。當充放電速率增加到1C時，當充放電循環達50圈後，空氣下熱處理之Li4Ti5O12薄膜電容量約163.9 mAhg-1，而還原氣氛熱處理之Li4Ti5O12薄膜電容量約
190.0 mAhg-1。

Since titanium ions show multi-valent states, the conductivity of lithium titanate may highly depend upon the addition of aliovalent dopant or surrounding atmosphere. To improve the electrical conductivity, introduce the Ti3+ through being calcined in reducing atmosphere. To improve the behavior of lithium ion diffusion, lattice expansed through the ionic radius of Nb5+ or Ti3+. The electrical conductivity of Li4Ti5O12 under reducing synthesis was improved by two orders of magnitude.The capacity and rate capability would be improved when exposed at low oxygen partial pressure.
Li4Ti5O12 thin films were deposited on a Pt/ Ti/SiO2/Si(100) substrate via radio frequency (rf) sputter in a mixture of oxygen and argon gases. The crystallinity of Li4Ti5O12 phase increased with the annealing temperature increasing from 500°C to 700°C. The variation was attributed to some Li escaped from thin films. The capacity of Li4Ti5O12 thin film was higher than the theoretical capacity (175 mAhg-1). It might attribute to amorphous TiO2 in the Li4Ti5O12 thin films. Li ions may be expected to react with H2O to Li2O, which decreased the capacity.

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