锂离子电池硅负极材料嵌锂结构及其性能演变

Structure and Properties of Si Electrodes with Lithium Insertion

利用第一性原理方法研究了锂原子在硅材料中的嵌入,考察了锂原子在不同的掺杂位点和掺杂浓度时掺锂体系的稳定性、结构变化、能带图和态密度图等。研究结果表明,锂原子在体硅材料中的掺杂方式是间隙掺杂而非取代掺杂,最稳定的嵌入位点是硅中四面体中心(Td)位点;当浓度达到12.5%时,体积膨胀率明显增大。随着锂原子的嵌入,体硅材料呈金属化特征。

Lithium ions inserting into Si material at various positions and at different doping concentrations was studied by first-principles method in this paper.The stability of different insertion sites,the structural changes,band structures and density of states after Li insertion were analyzed.It has been found that the lithium ions were doped as an interstitial atom rather than a substitutional one,and the tetrahedral center(Td)site is the most stable insertion position.When the concentration is larger than 12.5%,the system expansion rate increases obviously.From the band structure analysis,it can be seen that the Si material with the doped lithium ions becomes metal-like.