第一原理计算过渡金属掺杂尖晶石型LiMn_2O_4的电子结构

First Principles Calculation of Electronic Structure of Spinel Manganese Oxide Doping with Transition Metal

尽管对过渡金属掺杂锰酸锂后放电平台的升高现象有众多实验研究,但对其机理的研究却鲜见报道.采用第一原理的密度泛函理论,计算了过渡金属M(M=Ti、Cr、Fe、Co、Ni、Cu、Zn)掺杂尖晶石型LiMn2O4的电子结构,并以此分析放电平台的升高机理.电子态密度分析发现由于M-3d能带的诱导作用,出现了新的O-2p能带,而锂脱出时获得的电子,主要是由费米能级附近O-2p能带提供的.当过渡金属M由Ti变化到Zn时,M-3d能带逐渐向低能量的方向移动,新的O-2p能带出现的位置也随之下移,当Li脱出时,需要更多的能量才能从低能量的O-2p能带上获得电子,因而体系能够获得较高的嵌入电压.

Although there has been intensive research on improving the discharge voltage plateau of lithium manganese oxide doped by transition metals, there is a lack of corresponding studies on the improvement mechanism. In this paper, we investigate the electronic structure of spinel manganese oxide doping with transition metal M （M=Ti, Cr, Fe, Co, Ni, Cu, Zn） by first principles calculation based on the density functional theory. The calculated density of states indicates that a new O-2p band induced by the M-3d band appears at the exact position of the M-3d band itself. The compensating electrons are removed from the O-2p levels neighboring the Fermi level when the Li ion is removed. The position of the M-3d band shifts gradually to the low energy direction as M varies from Ti to Zn in the transition metal row of the periodic table, and the position of the new O-2p band also shifts downward following the M-3d band. The withdrawal of lithium electrons from this low O-2p band will result in high cell voltage.