Silicon-Carbon Nanotube Aerogel Core-Shell Nanostructures for Lithium-Ion Batteries with Long-Cycle Life and High Capacity

Abstract

Silicon anode for lithium ion battery (LiB) has been attracted considerable attention due to providing theoretical capacity up to about 10 times higher than that of conventional graphite. However, huge volume expansion during the cycle cause crack in the silicon, resulting in degradation of cycling performance and eventual failure. Moreover, low electrical conductivity and unstable solid electrolyte interface (SEI) layer aroused from repeated changes in volume still block the next step forward to commercialization of silicon material. Herein we demonstrate Si-carbon nanotube (CNT) aerogel core-shell nanostructure for LiB via freeze casting followed by RF magnetron sputtering process, exhibiting improved capacity retention as compared to Si only samples while 1,000 times of electrochemical cycle. The freeze casted CNT aerogel as 3D porous scaffold structures could provide buffer volume expansion/shrinkage of Si lattice upon cycling and increase electrical conductivity. In addition, the CNT aerogel could maintain the conducting network between pulverized Si materials during cycling. For this reason, after 1,000 charge/discharge cycles with high current densities (4.0 A g-1), Si@CNT aerogel anode yielded a high specific capacity of 1439 mAh g-1 with low capacity fade. Our approach could be applied to other LiB materials that go through large volume changes, and also affords promising potential for high performance energy applications.