Ni替代对锂离子电池材料LiMnTiO_4性能的影响

Effect of Nickle Substitution on the Performance of Lithium Ion Battery Material LiMnTiO_4

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。

Spinel LiMn1-xNixTiO4（x=0, 0.1, 0.2, 0.3） cathode materials were prepared by Sol-Gel method. The surface morphology and phase structure of LiMn1-xNixTiO4（x=0, 0.1, 0.2, 0.3） were characterized by FESEM and XRD. FESEM analysis indicated all the samples consisted of irregular particles and XRD patterns showed that all the materi-als had impurity TiO2, but there were no impurities related to Ni element. Electrochemical studies of doped and un-doped spinels were carried out by cyclic voltammetry （CV） and constant current charge-discharge. CV results showed that LiMnTiO4 had two couples of sharp redox peaks corresponding to Mn^3＋/Mn^4＋, Mn^2＋/Mn^3＋ redox reactions. How-ever, after Ni substitution, there appeared the third redox coupled, which was related to the Ni^3＋/Ni^4＋ redox reaction. LiMn1-xNixTiO4（x=0.1, 0.2, 0.3） exhibited improved electrochemical properties compared with LiMnTiO4. When the Ni substitution was 0.1, the first discharge capacity of LiMn0.9Ni0.1TiO4 was 171.6 mAh/gat current density of 30 mA/g, and after 48 charge-discharge cycles, the discharge capacity was 162.8 mAh/g, with the capacity retention of 82.7%. The Ex XRD pattern of LiMn0.9Ni0.1TiO4 showed that the material structure had no changes after the first cycle, and there was no transition between cubic phase and tetragonal phase.