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 SiO x –C dual-phase glass consisting of amorphous SiO x and free carbon phases and without Si–C bonds in SiO x phase. Dual-phase glass synthesis is achieved through a simple sol–gel route. The SiO x –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 SiO x phase well-disperses and dense-contacts with free carbon component at nanoscale level. The SiO x 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 SiO x component during discharge/charge process, which ensures an enhanced structural stability and an excellent cycling performance.