中文摘要：

通过分级共沉淀（分级进料）方法,结合高温热处理合成了金属元素（Ni,Mn）浓度从中心到表面呈梯度分布（中心富Ni,表面富Mn）的球形三元正极材料LiNi_（0.5）Co_（0.2）Mn_（0.3）O_2。利用X射线衍射（XRD）、场发射扫描电镜（FESEM）、能谱仪（EDS）和电感耦合等离子质谱仪（ICP-MS）等表征了所制备材料的成分、形貌和元素分布。通过恒流充放电和循环伏安、交流阻抗等方法对材料的电化学性能进行测试。结果表明,与传统的一级共沉淀方法相比,分级共沉淀所制备材料展现出更高的倍率性能（20 C放电比容量为104.1 m Ah·g（-1））、循环保持率（0.5 C循环200次容量保持率为95.8%）和快速充放电性能（20 C/20 C放电比容量为85.4 m Ah·g（-1））。这种分级进料制备技术可以有效提高共沉淀法制备锂离子电池三元正极材料的电化学性能。

英文摘要：

A stepwise co-precipitation route（precipitation with different ratios of Ni, Mn elements in three steps）has been adopted to synthesize the precursor of Ni_（0.5）Co_（0.2）Mn_（0.3）（OH）_2, which was mixed with Li_2CO_3 afterwards in a certain proportion. After post-heat treatment, the obtained LiNi_（0.5）Co_（0.2）Mn_（0.3）O_2 spherical cathode materials exhibit a gradient element distribution（nickel-rich in centre and manganese-rich around surface）. The structure, morphology and chemical composition of the samples were characterized by X-Ray Diffraction（XRD）, Field Emission Scanning Electron Microscopy（FESEM）, Energy Dispersive Spectrometer（EDS） and Inductively Coupled Plasma Mass Spectrometry（ICP-MS）, respectively. The electrochemical performances of the as-prepared LiNi_（0.5）Co_（0.2）Mn_（0.3）O_2 cathode materials were studied by galvanostatic charge/discharge measurements, Cyclic Voltammetry（CV） and Electrochemical Impedance Spectroscopy（EIS）. The testing results show that the materials derived from stepwise co-precipitation exhibit higher rate capability（104.1 m Ah·g（-1） at 20 C）, better cycle performance（with capacity retention of 95.8% after 200 cycles at 0.5 C） and more efficient fast charge and discharge performance（85.4 m Ah·g-1 at 20 C/20 C）, compared with the counterparts obtained from the conventional co-precipitation. In summary, this stepwise co-precipitation strategy is extremely promising for the preparation of LiNi_（0.5）Co_（0.2）Mn_（0.3）O_2 electrode materials with enhanced electrochemical performances.