薄膜厚度对LiMn2O4薄膜性质的影响

Influence of thickness on the properties of solution-derived LiMn2O4 thin films

采用溶液沉积法制备不同厚度的LiMn2O4薄膜，用x射线衍射及扫描电子显微镜检测和分析薄膜的物相及形貌；采用恒电流充放电及交流阻抗技术研究LiMn2O4薄膜的电化学性质。结果表明不同厚度的LiMn2O4薄膜均匀，晶粒大小相近，晶粒尺寸在20-50nm之间。当放电电流密度为100μA／cm^2时，不同厚度的LiMn2O4薄膜比容量相差不大，其值在42-47μAh／（cm^2．μm）之间。薄膜循环性能随着薄膜厚度的增加而变差，经50次循环后，薄膜每次循环的容量损失从0．18μm的0．012％升高到1．04μm的0．16％。电化学阻抗表明不同厚度的LiMn2O4薄膜的锂离子扩散系数差别不大，数量级为10^-11cm^2／s。

LiMn2O4 thin films of different thickness were prepared by solution deposition. The phase identification and surface morphology were studied by X-ray diffraction and scanning electron microscopy. The electrochemical properties of thin films were carried out by galvanostatic charge-discharge experiments and electrochemical impedance spectroscopy. The films of different thickness are homogeneous with the grain size between 20 and 50rim. The specific capacity of the films is between 42 and 47μAh/（cm^2.μm） at the discharge current density of 100μAh/cm^2. The capacity loss per cycle increases from 0.012% to 0.16% after being cycled 50 times as the thickness of thin film increases from 0.18μm to 1.04μm. The diffusion coefficients of lithium ion in the films of different thickness are close with the order of 10^-11cm^2/s.