通过共沉淀−高温固相法合成Li1.5Ni0.25Mn0.75O2.5固溶体正极材料，并通过溶液法对其进行LiAlO2包覆。采用X线衍射(XRD)、扫描电镜(SEM)、透视电镜(TEM)、电化学交流阻抗谱(EIS)和恒电流充放电测试分析样品的结构、形貌及电化学性能。研究结果表明：包覆前后样品都具备α-NaFeO2型层状结构；包覆后，Li1.5Ni0.25Mn0.75O2.5的循环稳定性和倍率性能都得到显著提高。包覆量为5%(质量分数)的样品性能最优。首次放电比容量为254.64 mA∙h/g。50次循环后，容量保持率由84.5%提高至98.9%。当倍率为10C时，包覆样品的放电比容量可达58.29 mA∙h/g，而未包覆仅为15.27 mA∙h/g。包覆5%LiAlO2的Li1.5Ni0.25Mn0.75O2.5正极材料具有最小的电荷转移阻抗。%Li1.5Ni0.25Mn0.75O2.5 was synthesized by co-precipitation and high temperature solid state reaction, and the LiAlO2-coated Li1.5Ni0.25Mn0.75O2.5 was synthesized by solid-solution. The structure, surface morphology and electrochemical performance of the samples were characterized by X-ray diffraction (XRD), scanning electron microscope(SEM), transmission electron microscope(TEM), electrochemical impedance spectroscopy (EIS) and galvanostatic charge-discharge testing. The results show that the samples deliver theα-NaFeO2 layered structure. After coating with LiAlO2, the cyclic stability and rate capability of Li1.5Ni0.25Mn0.75O2.5 are improved effectively. The sample coated with 5%(mass fraction) LiAlO2 exhibits excellent properties. First discharge specific capacity is 254.64 mA∙h/g. The capacity retaining ratio is increased from 84.5%to 98.9%after 50 cycles. The discharge capacity of LiAlO2-coated Li1.5Ni0.25Mn0.75O2.5 is 58.29 mA∙h/g at 10C, while that of pristine is only about 15.27 mA∙h/g. The sample coated with 5%(mass fraction) LiAlO2 has the lowest charge transfer impedance.
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