Insights into the conversion behavior of SiO-C hybrid with pre-treated graphite as anodes for Li-ion batteries

•SiO-C composite is prepared by a low-cost and simple method.•Pre-milling of graphite makes the components disperse more evenly.•Pre-milling of graphite enhances the conductivity of the SiO-C composite.•Cycling performance is improved by pre-milling of graphite.•Li4SiO4 and amorphous Si as the products of the 1st cycle are verified by HRTEM.

A SiO/graphite/amorphous carbon (SiO-C) hybrid anode with superior electrochemical performance is successfully realized by using a low-cost and simple method. Here, we apply a pretreatment of commercialized graphite by ball-milling to realize evenly dispersion of the components and good effect of carbon coating, thus resulting in excellent cycling stability. Specifically, the as-prepared sample shows a high reversible capacity of 850 mA h g−1 after 100 cycles at 100 mA g−1 and excellent rate capability of 730 mA h g−1 even at 500 mA h g−1. Additionally, a relatively high initial coulombic efficiency of 77% is delivered among SiO-based anode materials. High-resolution transmission electron microscope (HRTEM) technique is used to further visually verify the conversion behavior of SiO in the first cycle: scattered amorphous silicon particles with size about 5 nm and irreversible Li4SiO4 as the detected resultants. The result of electrochemical impedance spectroscopy (EIS) reveals that the polarization resistance (Rp) decreases with pre-treated graphite. This work presents a facile approach to prepare Si-based anode material for new generation lithium-ion batteries with high energy density and more insights into the conversion behavior of SiO.

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