掺F影响LiNi0.8Co0.1Mn0.1O2结构和性能的微观机制

以氟化锂为氟源,通过高温固相法合成了F掺杂的LiNi_(0.8)Co_(0.1)Mn_(0.1)O_2。采用X射线衍射仪(XRD)、扫描电镜(SEM)、X射线光电子能谱(XPS)和电化学测试等手段研究F影响LiNi_(0.8)Co_(0.1)Mn_(0.1)O_2结构和性能的微观机制。结果表明:适量F掺杂可以提高正极材料的放电比容量,改善其倍率性、循环性和热稳定性。当F掺杂量(物质的量分数)为1.5%时,材料的综合电化学性能最优,初始放电比容量(0.2C)和50周循环容量保持率(1C)分别由原始的174.0 mAh·g~(-1)(78.7%)提高到178.6 mAh·g~(-1)(85.7%)。LiNi_(0.8)Co_(0.1)Mn_(0.1)O_2材料性能的改善可归因于F能够增强过渡金属层、锂层与氧层之间的结合力,提高材料的结构稳定性。此外,F掺杂还有利于降低电化学反应中的界面电阻和电荷转移阻抗。

Microscopic Mechanism of Influence of Doping F on Structure and Performance of LiNi0.8Co0.1Mn0.1O2

The cathode material LiNi_0.8Co_0.1Mn_0.1O₂ for lithium ion battery was doped by F using a high temperature solid state method with lithium fluoride. The microscopic mechanism of F affecting the structure and performance of LiNi_0.8Co_0.1Mn_0.1O₂ was investigated by X-ray diffraction (XRD), scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS) and electrochemical measurements. The results show that appropriate dosage of F can increase the specific discharge capacity, rate capability, cycle performance and thermal stability of the cathode material. The optimum comprehensive performance of the material can be obtained at F molar fraction of 1.5%, the initial discharge specific capacity (0.2C) and capacity retention rate after 50 cycles (1C) were increased from the original 174.0 mAh·g^-1 (78.7%) to 178.6 mAh·g^-1 (85.7%), respectively. The improvement performance of the LiNi_0.8Co_0.1Mn_0.1O₂ cathode material by F doping can be attributed to the ability of F to enhance the bonding between the transition metal, lithium and oxygen layers, which improves the structural stability of the material. In addition, F-doping is beneficial to decrease the interface impedance and charge transfer impedance during the electrochemical reaction.