Ultrafine Si/C-graphite composite anode materials with improved cyclic performance

Si is of great interest as anode candidate for high energy-density lithium ion batteries. However, the rapid capacity fading and low first-cycle coulombic efficiency strongly hinder its applications. Ultrafine Si/C nanoparticles mixed graphite powders as composite anode materials have been synthesized through magnesiothermic reduction of ultrafine SiO2/C, and then mixed with graphite. Electron microscopy investigation indicates that the ultrafine Si/C particles with size ca. 10 nm are attached on the graphite surface. Electrochemical evaluation demonstrates that the cyclic performance of the ultrafine Si/C-graphite composite materials has been improved compared with Si and Si/C, in which the reversible capacity can reach 662.4 mAh g−1 with the first-cycle coulombic efficiency as high as 90.9%. Meanwhile, the capacity retention can reach 90.8% over 100 cycles. These ultrafine Si/C-graphite composite materials are promising anode candidate with combined electrochemical properties to meet multiple requirements of high energy-density lithium ion batteries.