Using first principles density functional theory, formation energies of lithium silicides were calculated. The formation of lithium silicides such as Li1Si1, Li12Si7, Li 2Si1, Li7Si2, Li15Si 4 and Li22Si5 were energetically favourable with potential decreasing. Li15Si4 calculated to be more stable than Li7Si2. Differences of Si-Si bond distances between 2.383 å of Li3.5Si as relatively good reversible range and 4.548 å of Li3.75Si 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.
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