An optimized 3D carbon matrix for high rate silicon anodes

Abstract

A free-standing 3D porous carbon matrix was fabricated by a solution-based self-assembly process, using graphene aerogel (GA) as the matrix and CNTs as the structural enhancer. CNTs, with high electrical conductivity and mechanical strength, formed into a 3D scaffold along with GA. Silicon particles, with an oxidation coating (Si@SiO_x), were embedded into this GA matrix, and twined around the CNTs to increase conductivity of the Si@SiO_x agglomerations and bonding force with the GA matrix. Electrodes constructed with the Si@SiO_x/CNTs/GA containing 44 wt% Si@SiO_x exhibit a stable storage capacity of 905 mA h g⁻¹ at 4 A g⁻¹ and 1500 mA h g⁻¹ at 0.1 A g⁻¹ after 150^th cycles with 93% capacity retention compared with the 10^th cycle capacity. These outstanding rate performances and cycling stability are attributed to the enhanced 3D porous matrix, which provides abundant internal space for volume changes of Si@SiO_x, easy penetration of electrolyte, fast electron and ion transfer speed, and high mechanical strength.