Lithium Alloying Potentials of Silicon as Anode of Lithium Secondary Batteries

摘要

Using first principles density functional theory, formation energies of lithium silicides were calculated. The formation of lithium silicides such as Li1Si1, Li_(12)Si7, Li2Si1, Li7Si2, Li_(15)Si4 and Li_(22)Si5 were energetically favourable with potential decreasing. Li_(15)Si4 calculated to be more stable than Li7Si2. Differences of Si-Si bond distances between 2.383 A of Li_(3.5)Si as relatively good reversible range and 4.548 A of Li_(3.75)Si as relatively low reversibility can be correlated to reversible lithiation range. Silicon is not only electron semi-conductor but also not good lithium ion conductor. Therefore during lithiation(delithiation) silicon has multi-level lithiated silicides to show broad and complicated XRD pattern.