SiO_x is one of the most promising anode materials for lithium-ion batteries (LIBs), due to its high theoretical capacity and low cost. However, the huge volume expansion and low electron/ion diffusion rate hinder its further commercial applications. Herein, a simple molecular polymerization method is developed to synthesize N,P co-doped SiO_x–C composites (denoted as SiO_x–C@CNT), in which SiO_x and carbon are uniformly dispersed at the atomic level, and the embedded carbon nanotubes improve the lithium ion diffusion kinetics. Benefiting from the unique structure, the SiO_x–C@CNT composites exhibit a high reversible capacity of 848 mA h g⁻¹ at 0.1 A g⁻¹ and long cycling stability (84.0% capacity retention after 1500 cycles). More impressively, the LiCoO₂∥SiO_x–C@CNT full battery also exhibits stable cycle life (only 4.7% capacity loss after 300 cycles at 1 C). These results show the application potential of the SiO_x–C@CNT anode in LIBs.