烧结气氛对无钴镍基正极材料LiNi0.7Mn0.3O2性能的影响

摘要

The LiNi0.7Mn0.3O2 cathode material was synthesized under different sintering atmosphere via co-precipitation and high temperature sintering method. The morphology, crystal structure, oxygen concentration, electrochemical performance and electrochemical impedance spectroscopy for LiNi 0.7Mn0.3O2 cathode material were characterized and tested by means of scanning electron microscopy (SEM), powder X-ray diffraction (XRD), oxygen analyzer, galvanostatic charge-discharge tests and electrochemical workstation. The results show that under the condition of whole sintering time in high purity oxygen atmosphere, the obtained material exhibits the best spherical morphology, the most complete layer structure, the best electrochemical performance and the smallest internal impedance. The initial discharge specific capacity of the material is as high as 191.0 mAh/g at 0.2 C within the voltage range of 2.75~4.35 V, the capacity retention ratio is 95.2 %after 70 cycles. But when the materials are synthesized in other sintering atmosphere, the initial discharge specific capacity are all below 184.0 mAh/g, and the capacity retention ratio are also all below 85 % after 70 cycles.%采用共沉淀-高温固相法，控制烧结气氛制备出LiNi0.7Mn0.3O2.借助扫描电子显微镜（SEM）、X射线衍射分析（XRD）、氧气分析仪、电池测试系统及电化学工作站对不同气氛条件下制备的LiNi0.7Mn0.3O2进行结构、形貌、固相反应过程氧气浓度变化、电性能和内阻的表征.研究结果表明，烧结过程存在2次明显吸氧阶段且全程通高纯氧制备的材料有更好的球形度，层状结构更完整，充放电性能及循环稳定性都更好，内阻也较小；在2.75~4.35 V电压范围内，以0.2 C进行充放电，其首次放电比容量高达191.0 mAh/g，70周循环后容量保持率为95.2%.烧结过程中由一种气氛切换为另一种气氛比烧结全程不通气或通空气所制备材料的性能差，但其首次比容量都低于184.0 mAh/g，70周循环后的容量保持率也都不足85.0%.