锂离子电池高镍三元正极材料LiNi0.8Co0.1Mn0.1O2的性能研究

富镍正极材料(LiNi0.8Co0.1Mn0.1O2)具有高容量的优点，是锂离子电池正极材料最有潜力的材料之一。为确定最佳合成条件，本工作研究了合成温度对材料性能的影响，并详细分析了材料电化学性能衰减的原因以及循环过程中材料结构的变化。采用热重/差示扫描量热法(TG/DSC)、X射线衍射(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(HRTEM)、能谱仪(EDS)、X射线光电子能谱(XPS)等手段对合成的正极材料进行了物化表征，并对其电化学性能进行测试。结果表明，在低温段500℃保温4 h，高温段750℃保温14 h合成的正极材料NCM750在0.2 C首次放电比容量为186.2 mAh/g，首次充放电效率为82.5%，1 C放电比容量为185.1 mAh/g，100次循环后仍有175.2 mAh/g，容量保持率为95.2%。在此条件下合成的材料具有结构稳定，粒径均匀，电化学性能优异等优点，本工作对富镍正极材料的合成及结构变化进行研究，有助于加深对材料的了解。

Research on the properties of LiNi0.8Co0.1Mn0.1O2 high nickel ternary cathode material for lithium ion batteries

The Ni-rich cathode material (LiNi0.8Co0.1Mn0.1O2) has the advantage of high capacity and is the most potential cathode material for lithium-ion batteries. However, the poor cycle performance and rate capability limit its application. In this work, the structure evolution of the cathode material during the synthesis process and the influence of manufacturing temperature on the material properties were studied, and the potential causes of the structural changes and electrochemical degradation of the cathode material during the cycle were analyzed in detail. The physicochemical characterizations were conducted by employing the thermal gravimetric/differential scanning calorimetry (TG/DSC), X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (HRTEM), energy dispersive spectrometer (EDS), X-ray photoelectron spectroscopy (XPS), etc. The cycle performance, rate performance, and other electrochemical properties were examined by electrochemical testing equipment. The results showed that the cathode material synthesized at 500℃ for 4 h and 750℃ for 14 h presents uniform particle size, good spherical structure, smooth surface of primary particles, compact arrangement, and stable crystal structure, which can alleviate polarization during cycling. Due to the proper particle size obtained at the optimized synthesis temperature, a relatively high initial discharge capacity, small volume changes, and slowly increased interfacial film resistance for the material were achieved, contributing to good Li+ diffusion kinetics. At 0.2 C, the first discharge-specific capacity was 186.2 mAh/g and the first charge-discharge efficiency was 82.5%. At 1 C, the discharge-specific capacity before and after 100 cycles were 185.1 and 175.2 mAh/g, respectively, and the capacity retention rate was up to 95.2%. The study of the synthesis and structural changes of Ni-rich cathode materials in this work can deepen the understanding of the materials and help improve the electrochemical performance of the materials.