LiCoO2/LiNi0.8Co0.15Al0.05O2混合正极的颗粒级配与电化学性能

通过机械球磨制备不同质量比的LCO/NCA混合正极材料，采用X射线衍射仪(XRD)和扫描电子显微镜(SEM)表征其相结构和微观形貌，研究了这种材料的电化学性能。结果表明，两种正极材料球磨混合后其晶体结构均未改变，但是初始的NCA球形二次颗粒被打散，形成的纳米粒子弥散填充在LCO微米颗粒的孔隙之间，提高了正极材料的涂膜密度和二者之间的接触紧密性。当LCO:NCA=6:4时混合正极材料具有最佳的颗粒级配效果，其首次充放电效率最高，为92.4%；在10 C (1 C=140 mA·g^-1)倍率下的比容量(136 mA·h·g^-1)是0.2 C时的78.0%，出现了明显的协同增强效果；在1 C倍率下循环100次其容量保持率为89.8%，表现出优异的电化学性能。

Electrochemical Properties of LiCoO2/LiNi0.8Co0.15Al0.05O2 Blended Cathode Materials with Varied Grain-gradations

Blended cathode materials LiCoO₂/LiNi_0.8Co_0.15Al_0.05O₂(LCO/NCA) with different mass ratios of LiCoO₂ to LiNi_0.8Co_0.15Al_0.05O₂ were prepared by ball milling method. The phase structure and morphology of the blended cathode materials were characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). The electrochemical properties of the prepared cathodes were examined in half cells. It follows that after the ball milling, the crystal structure of the blended cathode materials did not change, however, the initial secondary NCA microspheres were broken into nano-sized fragments, which were then uniformly filled into the gaps between LCO microspheres, resulting in enhancement of the contact between the two cathode materials, and therewith, the density of the film prepared on cathode. For LCO:NCA = 6:4, the blended cathode material displayed the best grain-gradation effect and good electrochemical performances: namely the initial columbic efficiency of 92.4%, the capacity retention of 78% at 10 C (1 C=140 mA·g^-1) referencing to that at 0.2 C, and capacity retention of 89.8% after 100 cycles at 1 C. A synergistic effect on the rate performance between the two cathode materials was obviously demonstrated.