β-MnO2和α-Mn2O3纳米棒的自牺牲模板法制备、 表征和应用

在150 ℃下, 仅以高锰酸钾溶液和无水乙醇为原料, 通过水热反应合成前驱体γ-MnOOH纳米棒. 以γ-MnOOH纳米棒为自牺牲模板, 分别在350和600 ℃下煅烧90 min, 制备出高纯度的β-MnO₂和α-Mn₂O₃纳米棒. 采用X射线粉末衍射(XRD)、 扫描电子显微镜(SEM)及热重分析(TGA)等对所制备的样品进行表征. 结果表明, 前驱物γ-MnOOH为高纯度的纳米棒状晶体, 直径约100~300 nm, 长度可达数微米, 且终产物β-MnO₂和α-Mn₂O₃均具有较高的纯度, 也很好地保持了前驱物的纳米棒状结构. 以二者为锰源, 通过固相反应合成出尖晶石LiMn₂O₄正极材料. 当充放电倍率为0.5 C时, 其首次放电比容量分别可达到120.4和123.9 mA·h/g, 而且表现出良好的循环性能和倍率性能.

Preparation of β-MnO2 and α-Mn2O3 Nanorods via a Self-sacrificing Template Route and Their Characterization and Application†

Pure-phased γ-MnOOH nanorods were synthesized at 150 ℃ for 20 h through a hydrothermal reaction process, during which KMnO₄ was reduced by CH₃CH₂OH under autogeneror pressure. With γ-MnOOH nanorods as self-sacrificing template, β-MnO₂ and α-Mn₂O₃ nanorods were prepared by calcining at 350 and 600 ℃ for 90 min, respectively. The materials were characterized by X-ray diffraction(XRD), scanning electron microscopy(SEM) and thermal-gravimetric analysis(TGA). The results showed that γ-MnOOH nanorods had good crystallographic quality and the diameters were about 100—300 nm, the length could be as long as several micrometers. The morphology and microstructure were well reserved in β-MnO₂ and α-Mn₂O₃ products and no other morphology of impurities was observed. With β-MnO₂ and α-Mn₂O₃ nanorods as manganese sources, spinel LiMn₂O₄ samples were prepared by solid state method. At the charge/discharge rate of 0.5 C, the LiMn₂O₄ samples could deliver the initial discharge capacities of 120.4 and 123.9 mA·h/g, respectively, and present good cycling stability and rate performance.