富锂锰正极材料中锰含量调控对其结构和电化学性能的影响

Effects of the Manganese Content on the Structure and Electrochemical Performance of Li-and Mn-rich Cathode Material

本研究通过调控富锂锰材料中Mn的含量对材料的电化学性能进行优化,采用简单高效的喷雾干燥结合高温煅烧制备了Li_(1.2)Ni_(0.13)Co_(0.13)Mn_(0.54+x)O_(2)(x=0~0.15)富锂锰正极材料,研究了Mn含量对材料的结构和首次库伦效率、循环性能、倍率性能及电压衰退等电化学性能的影响。发现Mn含量提高可在材料中生成一种具有高结构稳定性的Li_(4)Mn_(5)O_(12)尖晶石相,可有效提高材料的首次库伦效率和循环性能,随Mn含量的增加,材料的首次库伦效率和循环稳定性提高,但其容量有一定程度的下降。Mn含量的适量提高,对循环过程中放电电压的衰减基本没有影响,但若含量过高由于材料中尖晶石含量过高会引起较大的电压下降。本研究给出了优化的富锂锰正极材料成分,分析了相应电化学性能提高的机理。

In the present study,the electrochemical performance of the Li-and Mn-rich oxide cathode material is optimized by adjusting the content of Mn.Li_(1.2)Ni_(0.13)Co_(0.13)Mn_(0.54+x)O_(2)(x=0~0.15)(x=0-0.15)cathode materials are fabricated by a facile and high-efficiency method of spray drying coupled with a high temperature calcination.The effects of Mn content on the structure and the electrochemical properties,including the initial Coulombic efficiency,cyclic stability,rate-capability,voltage decay during cycling,have been studied.It is found that a Li_(4)Mn_(5)O_(12)spinel phase is formed in the material in the case of increasing Mn content,which results in effective enhancement on the initial coulombic and the cyclic stability.With the increase of Mn content,the initial Coulombic efficiency and cyclic stability increase continuously,but the capacity somewhat decreases.In addition,increasing Mn content within suitable amount has not visibly effect on the discharge voltage fading during cycling.However,excessive increase of the Mn content decreases the discharge potential to some extent as the formation of too high amount of spinal phase.The optimized composition for the Li-and Mn-rich layered oxide cathode material is obtained and the mechanism of the improved electrochemical properties is also proposed.