退火温度对LiMn_2O_4薄膜性能的影响

Effect of annealing temperature on structure, morphology and electrochemical property of LiMn_2O_4 thin films

以壳聚糖、聚乙烯吡咯烷酮(PVP)、醋酸锂和醋酸锰等为原料,采用溶胶凝胶-旋转涂布法在不锈钢基底上制备了LiMn2O4薄膜。通过X射线衍射光谱法(XRD)和扫描电子显微镜法(SEM)研究了退火温度对LiMn2O4薄膜的结构和形貌的影响,并研究了其电化学性能。结果表明:退火温度对薄膜的结构、形貌及电化学性能影响显著。在500～750℃下退火所制得的薄膜表面都呈现褶皱状的微观形貌,650℃以下退火的薄膜样品表面均匀致密,无裂痕。薄膜颗粒粒径随着温度的升高显著增大,结晶化程度也随之提高。650℃退火的薄膜样品为纯相尖晶石结构的LiMn2O4,并且具有最好的电化学性能,在50mA/cm2的电流下,初始比容量为35.9mAh/cm2·mm,经20次循环后比容量为33.8mAh/cm2·mm,容量保持了93.6%,表现出良好的循环性能。

Spinel LiMn2O4 thin films were prepared by sol-gel spin coating method coating the lithium/manganese acetates-containing precursor solution on a stainless steel substrate at different annealing temperatures. The structure and morphology of the thin films were investigated by XRD and SEM. The electrochemical property was also investigated. The results show that the structure, morphology and electrochemical property of the thin films are highly related to the annealing temperature. The surface morphology of thin films annealed at 500, 650, 700 ℃ and 750 ℃ respectively, all of them take on a wrinkle-like microstructure; with annealing at 650 ℃ or lower, the surface morphology is homogeneous and crack-free. The sizes of grains increase notably with the rise of annealing temperature,and so do the crystallization.When the annealing temperature rises to 650 ℃, the film is pure spinel LiMn2O4 and has optimal electrochemical property： its initial discharge special capacity is 35.9 μAh/cm^2 ·μm at 50 μA/cm^2. After 20 cycles, the discharge special capacity turns to 33.8 μAh/cm^2 ·μm, and 93.6% of capacity is kept.