Effects of In Situ Graphitic Nanocarbon Coatings on Cycling Performance of Silicon-Flake-Based Anode of Lithium Ion Battery

We coated graphitic nanocarbons by thermal chemical vapor deposition (CVD) on silicon flakes recycled from the waste of silicon wafer manufacturing processes as an active material for the anode of lithium ion battery (LIB). Ferrocene contains both iron catalyst and carbon, while camphor serves as an additional carbon source. Water vapor promotes catalytic growth of nanocarbons, including carbon nanotubes (CNTs), carbon fibers (CFs), and carbon films made of graphitic carbon nanoparticles, at temperatures ranging from 650 to 850 °C. The container of silicon flakes rotates for uniform coatings on silicon flakes of about 100 nm thick and 800–1000 nm in lateral dimensions. Due to short CVD time, besides CNTs and CFs, surfaces of silicon flakes deposit with high-density graphitic nanoparticles, especially at a low temperature of 650 °C. Nanocarbon coatings were characterized by SEM, EDX, ESCA, and Raman spectroscopy. Half-cells were characterized by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and retention of capacity in discharge/charge cycling. Silicon-flake-based anode with nanocarbon coatings at both 650 and 850 °C exhibited capacity retention of 2000 mAh/g after 100 cycles at 0.1 C, without needing any conductivity enhancement material such as Super P.