尖晶石锂锰氧结构中的氧缺陷及其修复方法

研究了氧缺陷型尖晶石锂锰氧化物的结构与电化学性能, 根据缺陷化学理论提出了弥补氧缺陷的办法. X射线衍射(XRD)结果表明, 在真空条件下于750 ℃焙烧不同时间后锂锰氧化物主要物相仍可保持尖晶石结构, 并伴随有少量Mn₃O₄和Li₂MnO₃杂相. 充放电测试及交流阻抗结果表明, 锂锰氧化物材料的放电容量随氧缺陷的增加而降低, 随着氧缺陷的增大, 表面膜阻抗及电荷传递阻抗增大、锂离子在锂锰氧固体中的嵌入与累积量减小使电化学性能恶化. 加入LiOH•H₂O和通入氧气焙烧可在一定程度上修复氧缺陷.

Oxygen Defects of Spinel Li-Mn-O Compounds and Methods to Remove Such Oxygen Defects

The structure and electrochemical properties of the spinel Li-Mn-O compounds with oxygen deficiency were investigated using X-ray diffraction (XRD), charge-discharge test and electrochemical impedance spectra (EIS). A method to remove oxygen deficiency was suggested in this paper. The XRD results indicate that the spinel Li-Mn-O compounds sintered at 750 ℃ under vacuum atmosphere for different hours mostly kept spinel structure with a few of Mn₃O₄ and Li₂MnO₃ impurities. The results of charge- discharge test and EIS showed that the specific capacities were decreased with increasing the amount of oxygen vacancy, and deterioration of the electrochemical properties could be contributed to the increase of the surface film resistance, charge-transfer resistance and the decrease of the intercalation capacities with the amount of oxygen vacancy. Sintering the samples with oxygen defects by addition of LiOH•H₂O or O₂ flowing can remove the oxygen deficiency inside the spinel Li-Mn-O compounds.