B掺杂尖晶石型LiMn2O4正极材料的制备及长循环电化学性能

采用固相燃烧法制备了单晶多面体尖晶石型LiMn1.94B0.06O4正极材料,利用X射线衍射(XRD)、扫描电镜(SEM)、透射电镜(TEM)以及充放电测试等手段,对其晶体结构和电化学性能等进行了表征。结果表明,B掺杂没有改变尖晶石型LiMn2O4的晶体结构,促进了(440)和(400)晶面的优先生长,形成了高暴露的(111)晶面及少部分(110)和(100)晶面的单晶多面体LiMn1.94B0.06O4晶粒,减少了Mn的溶解和提供了更多的锂离子扩散通道,其晶粒尺寸在160~350 nm之间。在10C、25℃的条件下,LiMn1.94B0.06O4电极的首次放电比容量可达到103.0 mAh·g^-1,2000次循环后,表现出较好的容量保持率(57.7%);在15C高倍率下,LiMn1.94B0.06O4仍然保持了67.1 mAh·g^-1的首次放电比容量,1500次循环后,仍能维持46.2%的容量保持率;在1C、55℃的条件下,其初始放电比容量高达125.2 mAh·g^-1,表现出良好的高温性能。B掺杂能够有效提高尖晶石型LiMn2O4的高倍率性能和循环寿命,稳定晶体结构,抑制Jahn?Teller效应和缓解Mn的溶解。

Preparation and Long Cycle Electrochemical Properties of B-Doped Spinel LiMn2O4 Cathode Material

A single crystal polyhedron LiMn1.94B0.06O4 cathode material was prepared by a solid?state combustion synthesis,their structural and electrochemical properties were characterized by X?ray diffraction(XRD),scanning electron microscopy(SEM),transmission electron microscopy(TEM)and charge?discharge test.The results show that Bdoping did not change the crystal structure of spinel LiMn2O4,and it could promote the preferential growth of(440)and(400)crystal facets.Inducing the formation of the single crystal polyhedron LiMn1.94B0.06O4 material with the highly exposed(111)facets and a small part of(110)and(100)facets,as well as a particle size of 160~350 nm,which enabled minimal Mn dissolution and provided more lithium ions channels.The LiMn1.94B0.06O4 delivered the initial discharge capacity of 103 mAh·g^-1 with a good capacity retention rate of 57.7%after 2000 cycles at 10C and 25℃.At high current rate of 15C,it showed the initial discharge capacity of 67.1 mAh·g^-1,and the capacity retention rates of 46.2%was obtained after 1500 cycles.Moreover,at 1C and high temperature of 55℃,the initial discharge capacity of 125.2 mAh·g^-1 was also maintained,showing good high temperature performance.The B?doping can effectively improve the high rate performance and cycle life of spinel LiMn2O4,stabilize the crystal structure,inhibit the Jahn?Teller effect and relieve the Mn dissolution.