采用溶胶-凝胶法结合固相反应制备了具有立方尖晶石结构的Li Mn1-xNixTi O4(x=0、0.1、0.2、0.3)锂离子电池正极材料。通过场发射扫描电镜(FESEM)观察材料的表面形貌,所制备的材料均呈现出典型的烧结体特征;用X射线衍射仪(XRD)分析材料的物相变化,Ni替代前后均产生杂相Ti O2,但没有产生与替代元素相关的杂相。通过循环伏安、恒电流充放电等测试研究样品的电化学性能。结果表明:Li Mn Ti O4有两对氧化还原峰,分别对应Mn3+/Mn4+、Mn3+/Mn2+的转变,而Ni替代后出现了额外的氧化还原对,即Ni3+/Ni4+的转变。Li Mn1-xNixTi O4(x=0.1、0.2、0.3)的电化学性能均优于Li Mn Ti O4,尤其当Ni替代量为0.1时,Li Mn0.9Ni0.1Ti O4在30 m A/g电流密度下的首次放电容量为171.6 m Ah/g,48次循环后容量为162.8 m Ah/g,容量保持率为82.7%。对Li Mn0.9Ni0.1Ti O4进行非原位XRD测试发现,材料一次循环后结构无明显变化,不存在立方相与四方相之间的转变。
An in situ method was designed to measure a continuous open circuit potential （OCP） curve of AZ31 magnesium alloy and to observe the morphology variation of Ni-P coating during the process of the electroless plating. The deposition mechanism of the electroless Ni-P plating on AZ31 Mg alloy was studied by OCP curve, scanning electron microscopy （SEM）, and energy dispersion spectroscopy （EDS）. The process of electroless Ni-P plating contains the coating formation stage and the coating growth stage. The formation stage includes three procedures, i.e., the nucleation and growth of Ni crystallites, the extension of the coating in two-dimensional （2D） direction and the coalescence of the coating along three-dimensional （3D） direction. SEM investigations demonstrate that the spherical nodules of the Ni-P coating are not only formed during the coating growth stage, but also generated in the initial deposition stage of electroless Ni-P plating. The variation of the coating rates at different deposition stages corresponds to the deposition mechanism of their respective deposition stage.
