锂离子电池富镍正极基础科学问题:径向有序多晶调控及机制

Basic scientific problems of nickel-rich cathode for lithium-ion battery:Regulation and formation mechanism of radially oriented parties

一次晶粒径向有序组装的颗粒结构能够较好抑制微裂纹的产生并提供良好的Li+扩散路径,是高端多晶富镍锂电正极材料理想的形态。近年来,研究人员通过对前驱体沉淀结晶和正极高温锂化结晶调控,获得具有较大长宽比晶粒有序组装的富镍正极材料。然而,关于富镍正极径向有序结构调控方法及形成机制的论述,特别是关于径向有序氢氧化物前驱体的调控方法、关键参数对有序结构的影响等并无详细的阐述。本文首先介绍了多晶富镍正极径向有序结构调控的必要性及其电化学性能提升的作用机制;其次,介绍了径向有序多晶富镍正极调控方法及形成机制,包括沉淀结晶过程关键参数(pH、氨浓度及固含量)对径向有序前驱体的影响、高温锂化过程温度及掺杂元素对正极继承前驱体径向有序性的影响;最后,对径向有序富镍正极调控面临的问题进行探讨,以期为相关专业人员开发富镍正极提供参考。

Secondary particle assembed with radial oriented primary grains can inhibit the formation of microcracks and provide a good Li+diffusion path,and it is an ideal morphology for high-end polycrystalline Ni-rich cathode materials.In recent years,some researchers have obtained nickel-rich cathode materials assembed with grains with large length-width ratio by regulating precursor precipitation crystallization and high temperature lithium crystallization.However,the regulation method and formation mechanism of the radially oriented structure of Ni-rich cathode,especially the regulation method of the radially oriented hydroxide precursor and the influence of the key parameters on the radially oriented structure,have not been elaborated.In this paper,the necessity of regulating the radially oriented structure of polycrystalline Ni-rich cathode and the mechanism on enhancing electrochemical performance are introduced.Secondly,the regulation method and formation mechanism of the radially oriented polycrystalline Ni-rich cathode are introduced,including the influence of the key parameters of precipitation crystallization process(pH,ammonia concentration and solid content)on the radially oriented precursor,and the influence of temperature and doping elements induced in calcination process on the maintenance of the oriented structure of precursor.Finally,the challenges facing for the regulation of radially oriented Ni-rich cathode are discussed.