(1. 哈尔滨工业大学(威海) 应用化学系，威海 264209；
2. 松山湖材料实验室，东莞 523808)
摘 要: 单晶型正极材料因其高循环性和高压实密度，已成为目前最有应用前景的材料之一。单晶材料是对二次球形颗粒的改进，了解单晶的形成和循环机制对单晶的制备有着很好的指导作用。本文首先分析了单晶材料的结构特征，单晶氧化物与球形二次颗粒氧化物都是层状结构；接着阐述了单晶的稳定性机理，单晶无内部晶界，在循环过程中不存在晶间破碎。本文还对单晶的形成和循环失效机理进行了总结，重点阐述单晶型正极材料在合成过程中溶解-再结晶的形成机理，即二次颗粒前驱体崩解，一次颗粒慢慢长大形成单晶颗粒；在循环过程中当截止电压小于4.3V时，晶内层间滑移可逆，多次充放电后存在滑移痕迹；当截止电压大于4.3V时，多次循环后出现晶内断裂，电池性能下降。
关键字: 锂离子电池；单晶；形成机理；失效机理；三元材料
（1. Department of Applied Chemistry, Harbin Institute of Technology, Weihai 264209, China;
2. Songshan Lake Materials Laboratory, Dongguan 523808, China）
Abstract:Single crystal cathode materials have become one of the most promising materials due to their high cycling and high pressure density. Single crystal material is an improvement on secondary spherical particles. Understanding the formation and cycling mechanism of single crystal has a good guiding role in the preparation of single crystal. In this paper, the structural characteristics of single crystal materials were firstly analyzed. Both single crystal oxides and spherical secondary particle oxides have layered structures. Then, the stability mechanism of single crystal was described. Single crystal has no internal grain boundary and there is no intercrystal breakage during the cycle. In this paper, the formation and cyclic failure mechanism of single crystal cathode materials were summarized. In addition, the formation mechanism of dissolution and recrystallization of the secondary particle precursor disintegrating and the primary particle gradually growing into the single crystal particle during the synthesis process of the single crystal cathode material was emphasized. When the cutoff voltage is less than 4.3 V, the slippage is reversible and there are slippage traces after multiple charging and discharging. When the cutoff voltage is greater than 4.3 V, the intragranular fracture occurs after several cycles and the battery performance deteriorates.
Key words: lithium-ion battery; single-crystal; formation mechanism; failure mechanism; ternary materials
