Disproportionated SiOx/C composite anode materials for lithium-ion batteries

A facile method to synthesize silicon oxide/graphite (SiOx/C) composite anode materials for high-capacity Li-ion batteries (LIBs) is proposed. In order to solve the problems of volume expansion and poor conductivity of silicon-based materials, ball milled disproportionate silicon oxide/graphite (m-d-SiOx/C) composite was successfully synthesized by combining high-temperature annealing and high-energy ball milling. LIBs with SiOx/C as anode material exhibit stable cycling performance at a current density of 100 mA g−1, with an initial reversible capacity of 1213.9 mA h g−1 and coulombic efficiency of 65.7 %. After 100 cycles, their reversible capacity is up to 1292.4 mA h g−1 with a coulombic efficiency of 99.7 %. The excellent electrochemical performance is attributed to the following facts: first, the disproportionated silicon oxide generates silicon and silicon dioxide, in which silicon plays a role in increasing the capacity, and silicon dioxide can irreversibly react with the electrolyte to form a buffer matrix, thereby alleviating the volume effect. Second, the high-energy ball milling not only greatly reduces the size of the commercially available silicon oxide, but also makes the disproportionated silicon oxide evenly adhere to the graphite surface. Graphite can make a partial capacity contribution while providing a conductive matrix for the composite.