Core-shell structured monodisperse carbon-rich SiO1.31C1.46H0.81 ceramic spheres as anodes for high-capacity lithium-ion batteries

摘要

SiOC ceramic material is a promising anode material for lithium-ion batteries. However, due to its intrinsically low electronic conductivity, it often suffers from a much lower specific capacity than the theoretical value, poor rate capability and serious potential hysteresis. In this paper, we report a core-shell structured monodisperse carbon-rich SiO1.31C1.46H0.81 submicron ceramic sphere with a free carbon content of 13.7 wt%, which is synthesized by directly annealing polysiloxane spheres derived from vinyltrimethoxysilane without adding external carbon resources. The SiO1.31C1.46H0.81 sphere has a unique microstructure, the core of which is organically assembled by large amounts of SiO1.31C1.46H0.81 primary particles of less than 20 nm and coated by a shell of 20-50 nm. As anodes for lithium-ion batteries, it presents much higher reversible capacity, initial Coulomb efficiency (ICE) and rate performance than the SiOC-based ceramic materials reported in the literature to date. At 100 mA g(-1), its first reversible capacity and ICE reach similar to 1107 mAh g(-1) and 78.2%, respectively. At 1600 mA g(-1), its stable discharge capacity is still as high as 610 mAh g(-1). The excellent electrochemical performance is attributed to the moderate composition, spherical morphology and unique microstructure of the synthesized material.