First-principles calculation of lithium insertion into homogeneous a-SiC2/5O6/5 as high performance anode

Abstract

Amorphous silicon oxycarbide is considered as a promising anode material for new generation of lithium-ion batteries, and figuring out the lithiation mechanism is crucial for its application. In this work, first principle calculations are performed to study the atomic structures, formation energy and lithiation voltage of homogeneous SiC_2/5O_6/5. The interpretation of radial distribution, angular distribution and coordinate number suggests that the Si–O bond tends to break and the Li₂O will form at the beginning of lithiation, then the Li_xO and the Li_ySi form with increasing Li concentration, which makes a major contribution to the capacity of SiC_2/5O_6/5. By the Li content dependence of the formation energies curve, the theoretical specific capacity of SiC_2/5O_6/5 is predicted as 1415 mA h g⁻¹, which is comparable to the reversible capacity of 900 mA h g⁻¹ in experiments. Both the formation energies and the voltage curves suggest lithium is preferable in incorporation with SiC_2/5O_6/5, and this is attributed to the formation of Li_xO and Li_ySi.