Glass-like Si–O–C composites have recently attracted considerable attention because of their potential as high capacity anode for rechargeable lithium ion batteries. However, the existence of Si–C bonds in Si–O–C phase restricts in a certain degree the electrochemical activity of silicon. Here, we demonstrate the synthesis and electrochemical performance of SiOx–C dual-phase glass consisting of amorphous SiOx and free carbon phases and without Si–C bonds in SiOx phase. Dual-phase glass synthesis is achieved through a simple sol–gel route. The SiOx–C dual-phase glass electrode delivers high reversible capacity of 840 mAh g−1 for 100 cycles and exhibits excellent rate-capability. The superior electrochemical properties can be attributed to the unique dual-phase glass structure that the amorphous SiOx phase well-disperses and dense-contacts with free carbon component at nanoscale level. The SiOx phase with a lower O/Si ratio contributes the high reversible capacity while the well-contacted free carbon provides a good electronic conductivity for electrode reaction. In addition, the free carbon component can alleviate the volume change of SiOx component during discharge/charge process, which ensures an enhanced structural stability and an excellent cycling performance.