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|Title: ||中孔洞碳材於高效能鋰離子電池之應用;Electrochemical Performance of Lithium Ion Batteries Based on Ordered Mesoporous Carbons|
|Keywords: ||中孔洞碳材;磷酸鋰鐵;二氧化錫;鋰離子電池;mesoporous carbon materials;lithuum iron phosphate;tin oxide;Lithium ion batteries|
|Issue Date: ||2015-09-23 10:50:43 (UTC+8)|
|Abstract: ||本論文主要探討規則中孔洞碳材CMK-8應用在鋰離子電極複合材料的相關研究，首先利用三嵌段共聚高分子型界面活性劑P123與矽源TEOS (Tetraethyl orthosilicate) 合成出Ia3 ̅d對稱性的Cubic KIT-6矽材，接著利用奈米膜鑄法合成出相同對稱性的CMK-8碳材，經過XRD、BET及TEM等鑑定後確認是高表面積且結構規則的中孔洞碳材。|
本論文第一部份將磷酸鋰鐵 (LiFePO4) 前驅物:醋酸鋰、硝酸鐵、85 %磷酸，用含浸水熱法含浸至規則中孔洞CMK-8碳材內 (分別使用了水和乙醇兩種溶劑)，不但抑制了LiFePO4晶體大小和雜相的生成，奈米尺寸晶體縮短了離子跟電子傳導路徑、CMK-8提供規則3維孔道，增加了擴散速率及整體材料在大電流充放電的結構穩定性，透過檸檬酸的添加，在0.05C充放速率下保有近100 %的效率及提升至166 mAh/g 高電容量，更能承受10C甚至更大電流的挑戰，此奈米複合材料極具應用的潛力!
第二部份將SnO2前驅物含浸至高規則CMK-8碳材孔洞中做負極應用，此複合材料有近40 %的高含浸量，電性結果顯示電容量比原來CMK-8高出許多，在0.05C第一圈放電有超過5000 mAh/g的電容量，之後的可逆電容量依舊非常高，庫倫效率幾乎維持在100%，循環次數多且耐大電流，非常適合用在大電容量產品上!!
;Rechargeable lithium-ion battery (LIB) is one of the most promising batteries, which is currently used in many portable electronic devices and electric vehicles. In recent years, there are some applications of mesoporous carbon materials as cathode for LIB. Olivine-structured LiFePO4 (LFP) has been the focus of research in developing low cost, high performance, environmental friendliness and high thermal stability. However, LFP is insulating in nature with a low electric conductivity of around 10−11 Scm−1 (compared with 10−3 Scm–1 for LiCoO2 and 10−5 Scm−1 for LiMn2O4), inducing low rate capacity. Therefore many efforts have been made to improve the electrochemical performance.
In this work, ordered mesoporous CMK-8 was introduced into the electrode active materials to achieve high electrochemical performance. The first part, different solvent and different ratio impregnation strategies are used to prepare high rate LFP with ordered mesoporous to contact the embedded LFP nanocrystal. CMK-8 ordered mesoporous carbon material (OMCs) is assembly of cubic ordered 3D structure, which has high surface area and suitable for facile impregnation. Mesopore is good for Li+ intercalation and deintercalation due to the short Li+ diffusion distance and a high lithium-ion flux across the electrolyte/solid interface. Base on half-cell testing, mesoporous nanocomposite LFP/C-CMK8-EtOH-05 achieved a high capacity of 166 mAh/g at 0.05C rate, and 121 mAh/g at 5C rate with good cycle life.
The second part, a hybrid material consisting of SnO2 nanoparticles (NPs) was embedded in the hard template CMK-8 as high capacity anode materials. It is observed that near 40 wt% of SnO2 particles with size between 3-5 nm are highly dispersed and homogeneously incorporated in the mesoporous channels and no bulky aggregates were found. The nanocomposite exhibits improved kinetics of lithiation–delithiation and high reversible capacity, and excellent cyclic stability without capacity loss over 200 cycles at 1C rate (780 mA/g) with a coulombic efficiency close to 100% after the initial cycle. This can be ascribed to the 3D-connected porosity and the confinement effect of the OMCs on the volume change of SnO2 NPs.
These results provide appropriate insight for improving the lithium storage performance of CMK-8 by accelerating the reaction kinetics and indicate that these composites have great potential to be applied in high-capacity and durable lithium ion batteries.
|Appears in Collections:||[化學研究所] 博碩士論文|
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