Li和Mg元素掺杂对锰基层状氧化物电化学性能的影响

Effects of Li and Mg Element Doping on Electrochemical Performance of Manganese-based Layered Oxides

采用固相反应法在900℃下制备了掺Li、Mg化合物Na_(0.75)Li_(0.25)Mn_(0.75)O_(2)和Na_(0.75)Mg_(0.25)Mn_(0.75)O_(2)。采用X射线衍射仪(XRD)和扫描电子显微镜(SEM)对所得材料的物相组成和形貌进行了表征;采用恒电流充放电和循环伏安法对材料的储钠性能进行了检测。实验结果表明,掺Li和掺Mg材料均呈现出层状形貌和P2型晶体结构。Na_(0.75)Li_(0.25)Mn_(0.75)O_(2)首次放电容量为146 mA·h/g,循环50次后容量保持率为79.4%;而Na_(0.75)Mg_(0.25)Mn_(0.75)O_(2)的首次放电容量达到158 mA·h/g,循环50次后容量保持率为64.1%。掺杂Li元素较掺杂Mg元素可更明显地提高材料的循环性能。

The Li-doped compound Na_(0.75)Li_(0.25)Mn_(0.75)O_(2) and the Mg-doped compound Na;Mg;Mn;O;were synthesized by solid reaction process.Phase composition and morphology of the obtained materials were characterized by using X-ray diffractometer(XRD) and scanning electron microscope(SEM).Sodium storage performance of the materials was tested by galvanostatic charge-discharge and cycle voltammetry.The experimental results show that both Li-doped and Mg-doped materials present layered morphology and P2 crystal structure.The initial discharge capacity of Na_(0.75)Li_(0.25)Mn_(0.75)O_(2)is 146 mA·h/g, and its capacity retention rate after 50 cycles is 79.4%.The initial discharge capacity of Na_(0.75)Li_(0.25)Mn_(0.75)O_(2) reaches 158 mA·h/g, and its capacity retention rate after 50 cycles is 64.1%.Doping with Li element can more significantly improve the cycle performance of the materials than doping with Mg element.