Carbon-confined PVA-derived silicon/silica/carbon nanofiber composites as anode for lithium-ion batteries

Novel silicon/silica/carbon (Si/SiO₂/C) composite nanofibers were synthesized by electrospinning and subsequent heat-treatment of a mixture of Si nanoparticles, sol-gel tetraethyl orthosilicate solution, and aqueous polyvinyl alcohol solution. These Si/SiO₂/C nanofiber composites were also coated with amorphous carbon by chemical vapor deposition (CVD) technique. The CVD carbon-coated nanofiber composites formed freestanding, conductive nonwoven mats that were used directly as binder-free anodes in lithium-ion batteries. Results indicated that the SiO₂ component of the composite anodes provided sufficient buffer function to accommodate the volume expansion of the Si nanoparticles and the CVD amorphous carbon coating helped maintain the Si nanoparticles within the carbon nanofiber matrix during repetitive charging and discharging processes. Electrochemical performance tests showed that the capacity retention of CVD carbon-coated Si/SiO₂/C nanofiber composites was greater than 91% and the corresponding coulombic efficiency was 97.4% at the 50th cycle.