LiFePO_4中对位缺陷的第一性原理研究

Antisite defect of LiFePO_4:A first-principles study

基于考虑了Fe-3d电子间的库仑作用U和交换作用J的GGA+U方案,应用第一性原理计算方法系统研究了LiFePO4的对位缺陷,以及对位缺陷的形成对材料的电导率和离子扩散速率的影响.结果表明,Li/Fe交换缺陷是最容易形成的,形成缺陷后的Fe—O键变长,扩宽了Li离子传输通道,有利于Li离子在通道中的扩散,对材料电化学性能的改善起到了一定的作用.

The antisite defect,electronic conductivity and ionic dynamic properties of LiFePO4 have been investigated using first-principles density functional theory taking into account the on-site Coulomb interaction within the GGA＋U scheme.Results indicate the Li/Fe exchange defect is the most preferred to occur in LiFePO4,which causes the Fe—O bond length to change in the direction favoring the formation of Li ＋ diffusion channels,hence improving the ionic dynamic properties of the olivine LiFePO4.