采用草酸盐共沉淀法制备了钠掺杂改性的Li0.98Na0.02Ni0.6Co0.2Mn0.2O2正极材料, 借助X射线衍射(XRD)、 扫描电子显微镜(SEM)、 透射电子显微镜(TEM)、 能量分散谱(EDS)、 感应耦合等离子体原子发射光谱(ICP-AES)、 电化学阻抗谱(EIS)和恒电流充放电测试等手段对材料的颗粒形貌、 晶体结构和电化学性能进行了研究.结果表明, 掺钠后的材料具有更完善的α-NaFeO2结构(空间群为R3m), 更低的Li+/Ni2+阳离子混排和更大的Li层间距, 易于Li+在晶格中的快速脱嵌迁移.电化学性能测试结果证实掺钠样品具有优异的循环稳定性和高倍率性能, 在2.7~4.3 V, 1C下循环100次后, 放电比容量仍为146 mA·h/g(容量保持率为95.4%), 在0.1C, 0.2C, 0.5C, 1C, 3C, 5C, 10C和20C时的放电比容量分别为181, 168, 162, 155, 143, 136, 126和113 mA·h/g.%Na-doped Li0.98Na0.02Ni0.6Co0.2Mn0.2O2 cathode material was synthesized through a simple oxalate co-precipitation.Powder X-ray diffraction(XRD), scanning electron microscopy(SEM), transmission electron microscopy(TEM), energy dispersive X-ray spectroscopy(EDS), inductively coupled plasma-atomic emission spectrometry(ICP-AES), electrochemical impedance spectroscopy(EIS) and galvanostatic charge-discharge tests were employed to analyze the particle morphology, crystal structure and electrochemical properties of the as-prepared materials.Results indicate that the Na-stabilized sample has a more ordered α-NaFeO2 structure(space group R3m), reduced Li+/Ni2+ cation mixing and enlarged Li layer spacing, which facilitates the fast insertion and extraction of Li+ ions in the bulk structure.Electrochemical results confirm that the Na-stabilized sample has excellent cycling stability and high rate performance.After 100 cycles at 1C between 2.7 V and 4.3 V, the cathode delivers a discharge capacity of 146 mA·h/g with capacity retention of 95.4%.At 0.1C, 0.2C, 0.5C, 1C, 3C, 5C, 10C and 20C, the specific capacities of the material are 181, 168, 162, 155, 143, 136, 126 and 113 mA·h/g, respectively.The Na-doping method is facile and feasible, which can provide some valuable reference for synthesizing other high rate and high capacity layered anode/cathode oxides.
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