Cr掺杂LiFePO_4导电性能的第一原理研究

First Principle Study on Conductivity of Cr-doped LiFePO_4

基于第一原理方法,由广义梯度近似(GGA)的密度泛函理论计算了Cr在Fe位掺杂的LiFePO4的电子结构,分析了不同掺杂量对晶胞参数,体积和费米能的影响。掺杂Cr后,系统的态密度图中费米能级移入导带;费米能级附近的价带和导带的峰强度增强;能带结构图中最低空轨道与最高占有轨道之间的能隙变窄,从LiFePO4的0.75 eV降至LiFe0.95Cr0.05PO4的0.62 eV。且上述现象在掺杂Cr含量较少时,变化更明显,表明少量的Cr掺杂有利于提高LiFePO4的导电性能,结果与实验相符。

Based on the first principle method,the electronic structures of Cr-doped LiFePO4 were calculated by density functional theory（DFT） of general gradient approximation（GGA）.The effects of Cr-doped LiFePO4 structures on the cell parameters,cell volumes and Fermi energies were analyzed.The calculated results show that the Fermi level of LiFe1-xCrxPO4 moves into conduction bands with Cr doping.The peak intensity of valence bands and conduction bands increases near the Fermi level.The band gap between LUMO and HOMO decreases from 0.75 eV（LiFePO4） to 0.62 eV（LiFe0.95Cr0.05PO4）.A small amount of doped Cr results in obvious effects on electronic structures,which indicates that the conductivity of LiFePO4 can be improved.The theoretical analyses are consistent with the experimental results.