二氧化鈦改質︰鋰離子電池負極材料; Titanium oxide modification:Anode of lithium-ion battery

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題名:	二氧化鈦改質︰鋰離子電池負極材料;Titanium oxide modification:Anode of lithium-ion battery
作者:	楊德敏;Te-min Yang
貢獻者:	化學研究所
關鍵詞:	二氧化鈦;鋰離子電池負極;Lithium-ion battery;Titanium oxide
日期:	2011-07-28
上傳時間:	2012-01-05 14:29:20 (UTC+8)
摘要:	動力型鋰離子電池需符合高能量密度與高功率兩要求。本研究目的在於提升鋰離子電池輸出功率，使其更適用於動力型電器。傳統鋰離子電池的負極材料-中間相碳微珠(MCMB)在大電流下進行充放電的表現不佳，奈米級二氧化鈦則展現具有做為高功率鋰離子電池負極材料的潛力。但該材料低電子導電度(10−9 to 10−7 S/cm)及低鋰離子擴散速率(10−15 to 10−13 cm2/s)造成應用之困難。為改進此材料的缺點，本研究探討了兩種改質的方案。增進活性物質的導電度，使得活性物質內的電荷轉移更加迅速且有效;或是提升活性物質的表面積以提升鋰離子嵌入量。為了實現上面兩個方案，本研究提供了兩種方法:第一是將二氧化鈦進行氮摻雜，形成具有良好導電度的氮化鈦。活性物質在氮化鈦協助下導電度提升了三個數量級，也使得電池的庫倫效率提升。二氧化鈦與氮化鈦混摻後提升了鋰離子在活性物質內的擴散係數，因此在10C (3.35A/g)電流下充放電還有35mAh/g的電容量；第二個設計是將二氧化鈦進行磷酸官能基化，磷酸化可抑制結晶區域的成長並維持活性物質的高表面積。在活性物質具高表面積下，鋰離子的嵌入量確實提高，首圈放電電容量達到250 mAh/g。但不幸的是，磷酸化的二氧化鈦不僅抑制結晶區域成長，更降低了銳鈦礦相的結晶度。導致鋰離子嵌入/脫出反應的可逆性不佳。此外也由慢速循環伏安法中了解到表面積與結晶區域大小確實影響鋰離子的嵌入量與極化程度。擁有高表面積(結晶區域小)的活性物質，鋰離子擴散速率高且極化現象並不顯著，因此在電池效能上有較好的表現。 power two requirements. The purpose of this research was to enhance the output power of lithium-ion battery and to make it more suitable for high power electrical. The traditional lithium-ion battery anode material - meso carbon micro beads (MCMB) demonstrates poor performance under high current charging / discharging. Nano titanium dioxide is a promising anode material for high power lithium-ion battery. However, the low electronic conductivity (10-9 to 10-7 S / cm) and low lithium ion diffusion rate (10-15 to 10-13 cm2 / s) makes it difficult to implement. Current research explores two designs to overcome these shortcomings. The first method is to enhance the electronic conductivity of active material which expedite the charge transfer. The goal is reached by doping titanium nitride with Titania oxide nano-particle. The structure not only raised the conductivity by three orders of magnitude, it also shows much better columbic efficiency. Titanium dioxide blends with titanium nitride also enhanced the lithium ion diffusion coefficient; therefore on the 10C (3.35A/g) current charging / discharging still retain 35mAh / g of capacity. The second design aims at increasing the surface area of the active material which improves the amount of lithium-ion intercalation. The goal is achieved by phosphatization of the titanium dioxide nanoparticle, which inhibits the growth of the crystalline domain and preserved higher active surface area. As a result, the discharging capacity in lithium-ion battery increases. Discharging capacity of the first cycle reached 250 mAh/g. Unfortunately, phosphatization of titanium dioxide created more amorphous region by reducing the anatase crystalline. Therefore, the reversibility in lithium-ion insertion / extraction is poor. In slow CV test we conclude that the surface area and the crystallite size affected both the amount of lithium-ion insertion and degree of polarization. Active material with high surface area (or smaller crystal size) shows faster lithium-ion diffusion rate but the polarization is not as obvious. Therefore, the battery shows better high-rate performance.
顯示於類別:	[化學研究所] 博碩士論文

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