“Nanoskeleton” Si-SiOx/C Anodes toward Highly Stable Lithium-Ion Batteries

Abstract

A fragile solid-electrolyte interphase (SEI) layer due to the volume expansion of silicon cannot sufficiently prevent side reactions and electrolyte consumption and restricts the application of silicon anodes in lithium-ion batteries with high cycling stability. Herein, a carbon nanotube (CNT) supported “nanoskeleton” structure with robust mechanical properties and improved conductive pathways is designed by twining CNTs with in situ grown SiO_x/C and carbon-wrapped Si nanoparticles. The CNT “nanoskeleton” can improve electrical contact between particles, promoting the formation of a denser and more homogeneous SEI layer. Moreover, the buffer region granted by the CNTs can tolerate the volume expansions of Si, avoiding the repeated destruction of the SEI layer during the continuous lithiation and delithiation processes. Combined with these advantages, the anode with optimal CNT content can deliver both a high capacity (918 mAh·g^–1 at 200 mA·g^–1) and high-capacity retention (74% after 300 cycles) with relieved volume expansion (71.4%). The capacity of the NMC111 full cell with the synthesized Si-SiOx/C anode is retained at 71 mAh·g^–1 after 500 cycles at 100 mAh·g^–1 with a capacity retention of 72%.