快速充電鋰離子二次電池負極複合碳材之研究

High-Rate Charge Composite Carbons for Li-ion Secondary Battery Anode Materials

李孟倫(Lee, Meng Lun)

指導教授 ： 施漢章 ； 葉均蔚

國立清華大學/工學院/材料科學工程學系/碩士(2009年)

https://doi.org/10.6843/NTHU.2009.00382

摘要

電動車(Electric vehicle, EV)已知為本世紀最重要的工業產品之一，而鋰離子二次電池(lithium ion secondary battery)將是電動車能源的首要選擇，就這方面的應用而言，快速充電的需求是首要挑戰和亟需解決的問題，近幾年來鋰鈦氧(Li4Ti5O12) 這種尖晶石(spinel)結構的化合物成了熱門的快速充電鋰離子電池負極材料，然而雖然其材料本身具有快速充電的特性，但卻存在著電壓太高的問題，如此一來，在和鋰離子電池正極配合時，因全電池電壓太低將造成應用範圍狹隘的問題。中間相碳球 (meso-carbon micro beads, MCMB) 長期以來用在商業用途上，具有穩定的電容量及放電特性，惟較缺乏快速充電的能力。本研究中擬結合上述兩種負極材料的優點，將MCMB的表面包附上奈米等級的鋰鈦氧材料，進行改質，利用sol-gel方式合成一種Li4Ti5O12/MCMB複合負極材料。改質過後的複合負極材料以X光繞射分析確認其結構，並使用掃描式電子顯微鏡(SEM)確認其表面型態，而將此材料製成電極版組成半電池進行電性測試發現，此Li4Ti5O12/MCMB複合負極材料具有快速充電(即高速率充電)特性，在4C充電時，可充入的電容量為160-170 mAh/g，而在6C充電條件下，電容量仍能維持在150mAh/g以上，並且在0.05C-6C的充電速率下，都具有0.3V左右的穩定電壓平台及平穩的放電曲線，經多次循環測試，此材料仍具有快速充電的能力，電容量仍可維持穩定，最後以交流阻抗(AC)以及循環伏安(CV)測試，驗證此材料組成電池之導電性及氧化還原反應的特性。

關鍵字

鋰離子二次電池

並列摘要

The electric vehicle (EV) is going to be one of the most important industries in this century, and the lithium-ion batteries should be the main choice of its power. High rate charging of lithium-ion battery is the major problem of this electric device. Recently, titanium-based compounds like spinel Li4Ti5O12 has become a popular anode material for the lithium ion battery, although it has a high-rate charging property but it also has a higher voltage plateau which is too high to an anode of general lithium ion batteries, and makes the application become narrow. MCMB (meso-carbon micro beads) is extended to be the anode material of the commercial lithium ion batteries for a long period of time, which is stable in voltage, capacity and cycle life performance, but without high-rate charging capability. In this study, we combine the advantages of these two materials, using the sol-gel process to modify the MCMB by coating Li4Ti5O12 to make a new material of Li4Ti5O12/MCMB composite anode. The phase of the produced Li4Ti5O12/MCMB composites particles was determined using powder x-ray diffraction (PXRD), and the grain size and morphology of the particle were examined through the field emission scanning electron microscope (FE-SEM). Some other tests are done for checking the electrochemical properties of the Li4Ti5O12/MCMB composites anode, it do shows the high-rate charging capability, while charging at 4C, the charging capacity is 160-170 mAh/g, and while charging at 6C, it still maintains the capacity over150 mAh/g. Under the charging rate of 0.05-6C, the Li4Ti5O12/MCMB composite anode can always show a flat voltage plateau at 0.3V, after several charging and discharging cycle, it still has a high-rate charging capability, and maintains a stable capacity. Finally, we use AC impedance and cyclic voltammetry analysis to test the oxidation and reduction of this material.

並列關鍵字

Lithium ion battery

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