無添加黏著劑之非晶五氧化二釩負極材料於鋰離子電池之電化學研究

Electrochemical study of binder-free amorphous vanadium pentoxide anode for lithium ion battery

甘能青(Neng-Ching Kan)

指導教授 ： 甘炯耀

國立清華大學/工學院/材料科學工程學系/碩士(2017年)

摘要

近年來隨著消費性電子產品的普及，使得二次儲能源件的需求與日俱增，其中具備高能量密度以及循環壽命的鋰離子電池在發展上最受人矚目。在商業化鋰離子電池負極材料中，金屬氧化物鈦酸鋰(LTO)具有相對碳材300倍的循環壽命以及快速充放電的特性，使其能夠在市場上脫穎而出。而在近期研究發現，五氧化二釩(V2O5)具有和LTO相同的儲鋰機制並擁有較高的嵌鋰量，更適合用於負極材料上。另外在晶體結構上，非晶態V2O5又相對結晶態有較好的可逆比電容。
本論文以非晶V2O5作為活性材料，利用水熱法直接沉積至多孔泡沫鎳集流片上，鋰離子電池測試結果顯示，在低電流密度0.5C充放電50圈後，可逆比電容仍可達884 mAh/g，且比電容維持率高達94.21%；然而在高電流密度1C充放電50圈後，比電容維持率僅剩77.74%，經由微分電容曲線比對後，發現充放電速率的改變主要影響低電位的比電容變化，相反的，衰退現象主要是在高電位的反應所主導。
另一方面，藉由和還原氧化石墨稀複合後，可提升1C充放電的比電容維持率至82%，並在交流阻抗分析中以時間常數模擬等效電路圖所代表的電化學反應，由時間常數的分析結果可得到在非晶V2O5和泡沫鎳之間的電荷傳輸阻抗Rct為影響電池穩定性的關鍵因素。

關鍵字

釩氧化物 ； 負極材料 ； 鋰離子電池

並列摘要

In recent years, as the popularity rate of consumer electronic product increases, the demand of secondary energy storage device increases. Among them, lithium ion battery(LIB) which possessed outstanding energy density and cycle life has gotten much attention. For the commercial anode materials of LIB, lithium titanate(LTO)metal oxide anode has shown 300 times the cycle life of carbon materials and higher charge/discharge rate, making it stand out from the market. In recent research, vanadium pentoxide(V2O5) has revealed the same lithium storage mechanism as LTO and has the higher amount of lithium intercalation than LTO, it’s more suitable for anode material. Moreover, amorphous V2O5 gets more reversible specific capacity than crystalline state.
In this thesis, we directly deposited amorphous V2O5 on porous nickel foam current collector by hydrothermal process. The LIB test demonstrates that after 50 cycles, the reversible specific capacity can reach 884 mAh/g and the retention can be maintained at 94.21% under low current density 0.5C. However, when the current density increases to 1C level, the retention decreases merely to 77.74% after 50 cycles. By taking differential capacity curves into comparison, we find the effect of charge/discharge rate that affects the low-voltage specific capacity. In contrast, the degradation of retention mainly takes place at high-voltage peak.
On the other hand, when amorphous V2O5 combined with reduced graphene oxide(rGO), it promotes the retention to 82% at a rate of 1C. Besides, through AC impedance analysis, the RC time constant model has been utilized to simulate the electrochemical reaction of equivalent circuit. Based on the result of time constant, the key point of charging/discharging stability is caused by the charge transfer resistance Rct between amorphous V2O5 and nickel foam interface.

並列關鍵字

vanadium oxide ； anode materials ； lithium ion battery

參考文獻

[1] Yoshino, A., The birth of lithium-ion battery. Angewandte Chemie 2012, 51(24), 5798-800.

[2] Chockla, A. M. et al. / ACS applied materials & interfaces 2012, 4(9), 4658-64

[4] Oh B. Chae et al. / Chem. Mater. 2014, 26, 5874−5881

[5] Xifei Li et al. / Electrochemistry Communications 12 (2010) 1222–1225

[6] X. H. Huang, J. P. Tu,z Z. Y. Zeng, J. Y. Xiang, and X. B. Zhao Journal of The Electrochemical Society, 155 _6_ A438-A441 _2008_