A facile synthesis of vanadium-doped SiOx composites for high-performance Li-ion battery anodes

Abstract

Abstract Silicon suboxide (SiOx) materials are excellent anode candidates for lithium-ion batteries (LIBs) and have attracted great attention currently because of their improved cycle performance and high specific capacity. Here, we demonstrate the application of a selective alcoholysis method to synthesize V-SiOx@C and Al-SiOx@C composites using SiCl4, ethylene glycol (EG), benzene, VCl4, and AlCl3. The preferred synthetic process uses SiCl4 and VCl4 or AlCl3 and dopes with V4+ and Al3+, including a homogeneous dispersion of V and Al ions. Meanwhile, in the alcoholysis process, the V-O-Si-H-C and Al-O-Si-H-C solution phase converts into solid phase V-SiOx@C and Al-SiOx@C composites, and the benzene skeleton crumbles into a carbon coating layer instead of dispersing. V doping and the carbon coating layer highly improve the electrochemical performance of SiOx. Moreover, the conductive carbon coating layer serves as a buffer and suppresses drastic structural collapse. The V-SiOx@C composite exhibits a high electronic conductivity of 1.46 × 10−3 S m−1, which is approximately two times higher than that of the Al-SiOx@C composite and SiOx@C. The V-SiOx@C composite exhibited a higher capacity and cycling stability compared to Al-SiOx@C composite and SiOx@C, and a large reversible capacity of 1305 mAh g−1 at a current density of 100 mA g−1, 1147 mAh g−1 (Al-SiOx@C) and 911 mAh g−1 (SiOx@C) at a 100 mA g−1 current density, and a capacity retention of ∼93% over 600 cycles at a current density of 1 A/g.