Vertical graphene growth on uniformly dispersed sub-nanoscale SiOx/N-doped carbon composite microspheres with a 3D conductive network and an ultra-low volume deformation for fast and stable lithium-ion storage

Abstract

Silicon suboxide (SiO_x, x < 2) is a promising candidate anode material, which has been widely used in lithium-ion batteries (LIBs) due to its high lithium-ion storage capacity. However, SiO_x has poor conductivity and undergoes large volume change, resulting in poor rate capability and stability during cycling. Herein, a vertical graphene@SiO_x/N-doped carbon (VG@SiO_x/NC) composite is easily prepared by the radially oriented growth of VG on SiOCN microspheres obtained by the pyrolysis of 1,3-bis(3-aminopropyl)tetramethyldisiloxane in a sealed vessel under thermal chemical vapor deposition (CVD) conditions. The SiOCN microspheres are transformed into SiO_x/NC microspheres with homogeneously dispersed SiO_x and NC at the sub-nanoscale in the CVD process. The uniformly dispersed sub-nanoscale NC in the spheres of SiO_x/NC and the surface VG construct a 3D conductive and robust network, resulting in fast and stable lithium ion intercalation/deintercalation. As an LIB anode, the VG@SiO_x/NC composite shows a high reversible capacity of 1323.8 mA h g⁻¹, excellent rate performance (265.5 mA h g⁻¹ at 20 A g⁻¹), and long cycling life (over 500 cycles with 84.2% of capacity retention at 2 A g⁻¹).