摻雜Mn之MoS2物性與製程鋰/鈉電池性能關係之研究

Studies of physical property in MoS2 doped with Mn uses in Lithium/Sodium battery

高振瑋(Cheng-Wei Kao)

指導教授 ： 楊仲準

中原大學/理學院/物理研究所/碩士(2017年)

https://doi.org/10.6840/cycu201700635

摘要

本論文以水熱製成Mo0.02Mn0.98S2二維結構的材料。X光繞射、XAFS與EDS實驗分析均顯示合成之樣品為純相結構，Mn可摻雜之最高比例為2%。TEM實驗顯示樣品之幾何形貌為堆疊之奈米薄片，且由1T與2H結構相無序交錯排列而成。
　　於拉曼光譜的實驗結果中，室溫下外加磁場會使拉曼峰偏移。在外加磁場變溫拉曼中分別在180 K與260 K有明顯強度的極大與次極大出現。由磁化率實驗發現低溫時沒有明顯的鐵磁性平台，表示樣品中具磁性之錳原子摻雜量較少或之間交互作用力太弱。在磁滯曲線上亦無明顯之矯頑力出現，顯示錳原子應均勻散佈於MoS2的晶體結構中。電性實驗顯示溫度與頻率主導樣品阻抗傾向於電阻性或是電容性。在40K時開始有一個金屬-絕緣轉變發生。將對數電導率與溫度倒數作圖可以得在200 K之上具有兩段線性區域，中間分隔的溫度為250K。其中低溫與高溫區之躍遷能量分別為82 meV與129meV。而此一轉折亦對應到拉曼光譜會受到外加磁場影響之溫度區間。
電池實驗結果中顯示MoS2與MoxMn1-xS2製備成鋰電池兩者均擁有良好的電容量。而製備成鈉電池時，電池允許之電容量皆下降，但摻雜Mn之MoS2樣品可具有較高的電容量與更佳的電池性能。

關鍵字

過渡金屬二硫化物 ； 二維材料

並列摘要

Series of two-dimensional MoxMn1-xS2 (x=0, 0.02, 0.04) materials were fabricated by hydrothermal method. Crystal structure and purity of resultants were firstly confirmed by XRD (x-ray diffraction), and also identified by XANES (x-ray absorption near edge spectroscopy) and EDS (energy dispersion spectroscopy). All experiments show that the allowed maximum proportion of Mn ions at Mo sites were 2%. TEM images displayed the morphology of all samples were nanoflowers that assembled by many nanosheets. Both 1T and 2H phases were observed simultaneously in x=0 and 0.02 samples.

Raman spectra show the peaks shift as an external magnetic field applied at room temperature. Two anomalies at 180K and 260K were found in the temperature profiles of peak positions in both zero and 0.1 T magnetic field. No any peak was found in the magnetic susceptibility measurements. There was also no coercivity found in the M-H curve at 2 K. These observations implied the dopant of Mn ions were dilute and spread uniformly at MoS2 crystal structure. The electric transport properties were strongly affected by temperature and frequency parameters. A metal-insulator transition was found at 40 K. The band gap was obtained by lnσ-T-1 plots. Between 200 K and 300 K, two linear sections that discontinue at 250 K were observed. The fitted band gaps below and above 250 K were 87 and 129 meV, respectively. This discontinue temperature was also found in the peak positions and intensities profiles of varied temperature Raman spectra.

Both x=0 and 0.02 samples exhibited excellent charge capacities and cycling life in making the anode of lithium battery, but not in sodium one. Otherwise, the Mn doped sample show a better capacity in sodium battery than pure MoS2 one.

並列關鍵字

MoS2 ； TMDs ； 2D material

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