A strategy of boosting the effect of carbon nanotubes in graphite-blended Si electrodes for high-energy lithium-ion batteries

Abstract

High capacity silicon (Si) has been added in graphite electrodes to overcome the theoretical capacity limit of the carbonaceous anode. However, different active materials that store Li+ ions via intercalation and alloying mechanisms are prone to suffer electrical disconnection due to the large gap derived from their different volume shrinkage ratios during delithiation. Herein, to address this poor compatibility on graphite-blended Si composite electrode (Gr-SC), a strategic usage of carbon nanotubes (CNTs) as electric bridge between graphite and Si is investigated through the comparison of three different types of Si blended graphite anodes (Gr-SC, Gr-SC with CNTs as additive, and Gr-MSC having implanted multi-walled CNTs on Si). Among the comparison group, the selectively located MW-CNT around Si in Gr-MSC exhibits outperformed capacity retention (98.4 %) and faster charge transfer kinetics after 50 cycles in a half cell, demonstrating a great compatibility between graphite and Si. This study presents a comprehensive understanding on the role of CNTs as an electric bridge on the electrode exploiting multiple Li storage mechanisms which undergo dissimilar volume change.