尖晶石LiCo_(0.05)Mn_(1.95)O_4体系EIS分析

Electrochemical impedance spectroscopy analysis of spinel LiCo_(0.05)Mn_(1.95)O_4

用溶胶-凝胶法合成了掺钴的尖晶石锰酸锂Li1.05Co0.05Mn1.95O4,由于Co3+的引入使得材料结构更加稳定,循环稳定性增强。材料在0.1 C下首次放电比容量为105.2 mAh/g,循环20次后为104.3mAh/g,容量保持率为99.1%;1 C下首次放电比容量为92.4 mAh/g,循环20次后放电比容量为91.1mAh/g,容量保持率为98.5%。电池在充电前电荷转移电阻Rct很大,锂离子扩散系数较小,1 C循环结束后电极的电荷转移电阻Rct最大为225.2Ω,0.5 C循环结束后电极的锂离子扩散系数DLi+最大为6.16×10-5m2/s。

Co-doping spinel Li1.05Co0.05Mn1.95O4 was synthesized by sol-gel method.Owing to the introduction of Co^3＋,the structure of the material was more stable and the cyclic stability was enhanced.At 0.1 C,LiCo0.05Mn1.95O4 powder possessed the initial discharge capacity of 105.2 mAh/g and it was 104.3 mAh/g after 20 cycles,the capacity retention rate was 99.1%.At 1 C,the initial discharge capacity was 92.4 mAh/g and it was 91.1 mAh/g after 20 cycles,the capacity retention rate was 98.6%.The charge-transfer resistance which reduced gradually with the cycles was large before charging.After the cycles at 1 C,the charge-transfer resistance was 225.2 Ω,larger than others（0.1 C,0.2 C,0.5 C）;and after the cycles at 0.5 C,the lithium ion diffusion coefficient was 6.16×10^-5 m^2/s,larger than others（0.1 C,0.2 C,1 C）.