Understanding the high rate lithium storage capabilities of SiCO-derived porous carbon

Abstract Porous carbon is of significant interest as a new generation of anode material for lithium-ion batteries because of its superior cycling performance. However, very little is known about the mechanism underlying these excellent properties at the atomic-scale. In this work, various atomic structures of porous carbon are successfully obtained by simulating the etching process of silicon oxycarbide (SiCO) with varying carbon content; in addition, the atomic mechanism for high rate lithiation in the porous carbon is investigated by first principles calculations. Our calculation results show that the formation of Li-silicate and LixO complexes is related to irreversible lithium loss. However, the small voids generated from the breaking of the carbon network and the LixO-filled pores make major contributions to the easy intercalation and fast diffusion of lithium in the porous structure. SiCO-derived porous carbon presents a unique atomic structure with an optimal void size of 0.4–0.6 nm, thus explaining its superior cycling performance in experiments. Our analysis of the lithiation process provides a conceptual foundation for future design of porous carbon-based anode materials.