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采用溶胶-凝胶法合成钠离子电池正极材料Na(Mn0.4Fe0.2Ni0.4)O2,并对其进行Mg元素掺杂合成Na(Mn0.4Fe0.2Ni0.35Mg0.05)O2材料,分别对2种材料的表面形貌、结构以及电化学性能进行了研究.结果表明:掺杂合成的样品Na(Mn0.4Fe0.2Ni0.35Mg0.05)O2同样具有O3型层状结构,虽然首次放电比容量降低至125.6 mAh/g,但是其循环性能和倍率性能却明显优于原始样品.在循环50次之后,其放电比容量仍可达114.7 mAh/g,对应的容量保持率为91.3％.在1C倍率下,仍能释放出90.1 mAh/g的可逆容量.此外,交流阻抗结果表明,该材料具有更小的电荷转移阻抗.“,”Na(Mn0.4Fe0.2Ni0.4)O2 and Na (Mn0.4Fe0.2Ni0.35Mg0.05)O2 are synthesized by a sol-gel method and used as cathode materials for sodium ion batteries.The morphology,structure and electrochemical performances of the samples are investigated by scanning electron microscope,X-ray diffraction and charge-discharge test.The results manifeste that the O3-type structure remains unchanged after substitution.The magnesium-substituted sample,Na(Mn0.4 Fe0.2Ni0.35Mg0.05)O2,exhibits improved capacity retention and rate performance at the price of the initial reversible capacity.The initial discharge capacity is 125.6 mAh/g and the capacity retention is 91.3％ after 50 cycles at the current density of 10 mA/g.Even at a high discharge rate of 1 C,it still delivers a discharge capacity of 90.1 mAh/g.Electrochemical Impedance Spectroscopy (EIS) measurements demonstrate that the charge transfer resistance of Na (Mn0.4Fe0.2Ni0.35Mg0.05) O2 is smaller than the pristine sample.