掺Cr尖晶石LiCr_xMn_(2-x)O_4材料EIS研究

Electrochemical impedance spectroscopy of Cr-doping spinel LiCr_xMn_(2-x)O_4 cathode material

用溶胶-凝胶法合成了尖晶石LiCrxMn2-xO4（x=0.05,0.1,0.2,0.3,0.4）正极材料,通过恒流充放电和电化学阻抗谱研究了Cr掺杂改性LiMn2O4的电化学性能。结果表明,Cr掺杂可提高LiMn2O4的循环稳定性,当Cr掺杂量为0.2时,LiCr0.2Mn1.8O4具有最高比容量110 mAh/g,循环50次后其容量几乎没有下降。LiCr0.1Mn1.9O4正极在首次充电过程中,当电极电位在3.85~4.15V之外时其EIS谱高频区的半圆和中频区的圆弧发生融合;等效电路的拟合研究发现,随着电极电位的升高,RSEI逐渐增大,表明充电过程中尖晶石LiCr0.1Mn1.9O4正极上SEI膜的厚度是随极化电位的升高而变厚;Re随电极极化电位的升高总体上是减小;而Rct随电极电位升高或降低表现为先减小,后增大。

In this paper Cr-doping spinel LiCrxMn2-xO4 cathode material was synthesized by sol-gel method and its electrochemical properties were researched by constant-current charge-discharge and electrochemical impedance spectroscopy（EIS） methods.The cycle stability of LiMn2O4 doped with Cr improved significantly.LiCr0.2Mn1.8O4 material had the highest specific capacity（110 mAh/g）,which almost had no loss after 50 cycles.When electrode potential was outside the range of 3.85~4.15 V,the high frequency semicircle and middle frequency arc integrated gradually during the first charge-discharge process of LiCr0.1Mn1.9O4.By an appropriate equivalent circuit proposed,with the electrode potential increasing,RSEI increased by degrees,which indicated that the thickness of solid electrolyte interface film（SEI） of LiCr0.1Mn1.9O4 cathode increased with electrode potential increasing during the charge process.Overall the Re reduced with the increasing of electrode polarization potential,but the Rct first decreased and then increased with the electrode polarization potential increasing or decreasing.