Dopant Modulated Li Insertion in Si for Battery Anodes: Theory and Experiment

We examine the effects of p-type and n-type dopants on the lithiation of crystalline Si as related to Li-ion batteries. In situ Raman spectroscopy and electrochemistry are used to investigate two crystallographic faces, (100) and (111), for boron (B) and phosphorus (P) dopants, to monitor the insertion of Li and the associated transition to amorphous Si. Density functional theory calculations are used to investigate the lithiation of doped and undoped crystalline Si bulk and surface models. The experimental and computational results suggest that lithiation voltages are different for P-doped and B-doped Si. The B-doped surfaces are found to insert Li at higher voltages than P- and undoped surfaces but result in less Li insertion. These results provide an understanding of the effects on dopants on the lithiation of silicon which may ultimately aid in the development of alternate anode materials for Li-ion batteries.