SiOx@C composites obtained by facile synthesis as anodes for lithium- and potassium-ion batteries with excellent electrochemical performance

Low silicon oxide (SiO) is a promising anode material for lithium and potassium ion batteries due to its high theoretical capacity (~2400 mAh g−1) and good cycle performance. However, volume effects and poor intrinsic electronic conductivity during cycling limit its practical application. To meet this challenge, we synthesized SiOx@C (SC) anodes with various carbon contents by ball milling and high-temperature carbonization. The graphite/asphalt coating reduces the volume expansion of SiO and reduces the mechanical stress. When used as a lithium ion battery (LIB) electrode, the SC-2 material retained a lithium storage capacity of 729.5 mAh g−1 after 200 cycles at a current density of 200 mA g−1. In addition, when used as a potassium ion battery (KIB) electrode, the SC-2 material provides a high capacity with a discharge capacity of 107.0 mAh g−1 after 400 cycles at 200 mAh g−1 and excellent cycle life (after 2000 cycles at 500 mA g−1, the capacity 80.8 mAh g−1 was retained). The potassium storage mechanism of the SC electrode was analyzed by the simple ex-situ XRD technique. These results show that SC anodes are promising for application as anode materials for LIBs and KIBs.