Carbon-coated silicon nanoparticle-embedded carbon sphere assembly electrodes with enhanced performance for lithium-ion batteries

Abstract

The uniform dispersion of Si materials in a carbon matrix while maintaining the nanomorphology of Si is required to achieve higher performance lithium-ion batteries (LIBs). Carbon-coated silicon nanoparticles embedded in monodisperse carbon spheres (C-SNP/CSs) were assembled by a simple mixing approach. We obtained high silicon contents up to 56 wt% for the composite electrodes. The C-SNP/CS anodes delivered a reversible specific capacity of 1230 mAh g (1) for 56 wt% Si and 953 mA h g (1) for 44 wt% Si at 800 mA g (1) after 150 charge/discharge cycles. The capacity retention after 150 cycles was 73% for the 56 wt% Si and 86% for 44 wt% Si C-SNP/CS electrodes, while the bare C-SNPs without CSs displayed only 32% retention. The high cycle performance indicates that the CSs effectively alleviated the mechanical stress induced by the large volume changes of Si during the charge/discharge cycles. Moreover, the high capacity retention reveals the high electrical conductivity of the electrodes, provided by the assembled morphology the CSs and the carbon-shell on the silicon nanoparticles(SNPs). The use of CSs with C-SNPs is a facile method to obtain a uniformly-dispersed mixture and can be readily scaled for practical applications.