Influence of carbon coating on the electrochemical performance of SiO@C/graphite composite anode materials**Project supported by the State Grid Technology Project, China (study on the mechanism and characterization of lithium dendrite growth in lithium ion batteries, Project No. DG71-17-010), the National Key Research and Development Program of China (Grant No. 2017YFB0102004), and the National Natural Science Foundation of China (Grant No.

Abstract

Silicon monoxide (SiO) has been considered as one of the most promising anode materials for next generation high-energy-density Li-ion batteries (LiBs) thanks to its high theoretical capacity. However, the poor intrinsic electronic conductivity and large volume change during lithium intercalation/de-intercalation restrict its practical applications. Fabrication of SiO/C composites is an effective way to overcome these problems. Herein, a series of micro-sized SiO@C/graphite (SiO@C/G) composite anode materials, with designed capacity of , are successfully prepared through a pitch pyrolysis reaction method. The electrochemical performance of SiO@C/G composite anodes with different carbon coating contents of 5 wt%, 10 wt%, 15 wt%, and 35 wt% is investigated. The results show that the SiO@C/G composite with 15-wt% carbon coating content exhibits the best cycle performance, with a high capacity retention of 90.7% at 25 °C and 90.1% at 45 °C after 100 cycles in full cells with LiNi0.5Co0.2Mn0.3O2 as cathodes. The scanning electron microscope (SEM) and electrochemistry impedance spectroscopy (EIS) results suggest that a moderate carbon coating layer can promote the formation of stable SEI film, which is favorable for maintaining good interfacial conductivity and thus enhancing the cycling stability of SiO electrode.