Ni-Cu双掺LiMn2O4正极材料的制备及电化学性能研究

Preparation of Ni-Cu co-doped LiMn2O4 cathode material and study on its electrochemical properties

通过简易的无焰燃烧法合成了LiMn2O4、LiNi0.08Mn1.92O4和LiNi0.08Cu0.05Mn1.87O43种正极材料。利用XRD、SEM、恒电流充放电测试等手段对合成材料的结构、形貌和电化学性能进行了表征。结果表明,所制备的3种正极材料均为立方尖晶石结构;Ni-Cu共掺杂提高了LiNi0.08Cu0.05Mn1.87O4材料的晶体结构稳定性,表现出比LiNi0.08Mn1.92O4和LiMn2O4材料较好的倍率性能和循环寿命。在室温和1 C倍率下,LiNi0.08Cu0.05Mn1.87O4样品的首次比容量为104.7 m A·h/g,循环200次后的容量保持率为81.38%;在较高的倍率5 C循环1000次后,容量保持率为68.23%;即使在高温55℃和1 C倍率下,仍可获得较高的首次放电比容量,为110.8 m A·h/g,200次循环后的容量保持率为56.23%。CV和EIS测试结果表明,LiNi0.08Cu0.05Mn1.87O4具有较好的循环可逆性和较小的电荷转移阻抗。

LiMn2O4,LiNi0.08Mn1.92O4 and LiNi0.08Cu0.05Mn1.87O4,three kinds of cathode materials,are synthesized by a facile flameless combustion method.XRD,SEM and galvanostatic charge/discharge test are employed for the characterization and measurement of crystalline structure,morphology and electrochemical properties.Results show that these three as-prepared cathode materials have a cubic spinel structure.Ni-Cu dual-doping enhances the crystal structure stability of LiNi0.08Cu0.05Mn1.87O4 sample,which hence exhibits better rate performance and cycle life than LiNi0.08Mn1.92O4 and LiMn2O4.At a current rate of 1 C and room temperature,LiNi0.08Cu0.05Mn1.87O4 has a first-discharge specific capacity of 104.7 m Ah·g^-1 and a capacity retention rate of 81.38%after 200 cycles.At a current rate of 5 C,its capacity retention rate can remain 68.23%after 1000 cycles.Even at 55℃and 1 C rate,LiNi0.08Cu0.05Mn1.87O4 still delivers a first discharge specific capacity of 110.8 m Ah·g^-1 and a capacity retention rate of 56.23%after 200 cycles.CV and EIS tests demonstrate that LiNi0.08Cu0.05Mn1.87O4 displays better cycling reversibility and smaller charge transfer impedance.