关键词: 锂离子电池, 富镍正极材料, 浓度梯度, 改性

Abstract:

With the advantages of high specific capacity, low cost, environmental protection and no need for high-voltage electrolyte, nickel-rich oxide cathode materials have attracted much attention. Although the higher Ni content contributes to improve the specific discharge capacity, it also produces cationic mixing, surface and interface reactions and crack propagation which leads to structural instability, etc., resulting in poor cycle life, low thermal stability and poor storage performance of nickel-rich cathode materials, which hinder their commercial application. In order to give full play to the advantages of nickel-rich LIBs, nickel-rich oxide cathode materials have been carried out varieties of modifications. In the past decade, nickel rich cathode materials have experienced the development stages of ion doping, surface coating, single crystal, core-shell structure, concentration-gradient structure and so on. In this paper, the mechanism and research progress of doping, coating, single crystal and core-shell structure modification were briefly reviewed, and the edges and inherent shortcomings of these methods were analyzed. After that, this paper focused on the analysis of the concentration-gradient materials, which were divided into three parts according to their development stages: nickel-rich core with concentration gradient shell, linear concentration gradient materials and progressive concentration gradient materials. The synthesis methods, modification mechanism and electrochemical performance of them were introduced in detail. In a comprehensive view, the concentration gradient material can fundamentally solve the inherent weaknesses of nickel rich cathode materials, and it was believed that this technology would play an important role in the practical process of nickel rich cathode materials.

Key words: lithium ion battery, nickel-rich cathode material, concentration gradient, modification